mirror of
https://github.com/pointfreeco/swift-composable-architecture.git
synced 2025-12-20 09:11:33 +01:00
774 lines
28 KiB
Swift
774 lines
28 KiB
Swift
import Combine
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import Foundation
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/// A store represents the runtime that powers the application. It is the object that you will pass
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/// around to views that need to interact with the application.
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///
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/// You will typically construct a single one of these at the root of your application:
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///
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/// ```swift
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/// @main
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/// struct MyApp: App {
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/// var body: some Scene {
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/// WindowGroup {
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/// RootView(
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/// store: Store(initialState: AppFeature.State()) {
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/// AppFeature()
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/// }
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/// )
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/// }
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/// }
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/// }
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/// ```
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///
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/// …and then use the ``scope(state:action:)-9iai9`` method to derive more focused stores that can be
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/// passed to subviews.
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///
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/// ### Scoping
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///
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/// The most important operation defined on ``Store`` is the ``scope(state:action:)-9iai9`` method, which
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/// allows you to transform a store into one that deals with child state and actions. This is
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/// necessary for passing stores to subviews that only care about a small portion of the entire
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/// application's domain.
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///
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/// For example, if an application has a tab view at its root with tabs for activity, search, and
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/// profile, then we can model the domain like this:
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///
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/// ```swift
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/// struct State {
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/// var activity: Activity.State
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/// var profile: Profile.State
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/// var search: Search.State
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/// }
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///
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/// enum Action {
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/// case activity(Activity.Action)
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/// case profile(Profile.Action)
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/// case search(Search.Action)
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/// }
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/// ```
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///
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/// We can construct a view for each of these domains by applying ``scope(state:action:)-9iai9`` to a
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/// store that holds onto the full app domain in order to transform it into a store for each
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/// sub-domain:
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///
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/// ```swift
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/// struct AppView: View {
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/// let store: StoreOf<AppFeature>
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///
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/// var body: some View {
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/// TabView {
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/// ActivityView(
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/// store: self.store.scope(state: \.activity, action: AppFeature.Action.activity)
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/// )
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/// .tabItem { Text("Activity") }
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///
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/// SearchView(
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/// store: self.store.scope(state: \.search, action: AppFeature.Action.search)
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/// )
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/// .tabItem { Text("Search") }
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///
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/// ProfileView(
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/// store: self.store.scope(state: \.profile, action: AppFeature.Action.profile)
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/// )
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/// .tabItem { Text("Profile") }
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/// }
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/// }
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/// }
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/// ```
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///
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/// ### Thread safety
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///
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/// The `Store` class is not thread-safe, and so all interactions with an instance of ``Store``
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/// (including all of its scopes and derived ``ViewStore``s) must be done on the same thread the
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/// store was created on. Further, if the store is powering a SwiftUI or UIKit view, as is
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/// customary, then all interactions must be done on the _main_ thread.
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///
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/// The reason stores are not thread-safe is due to the fact that when an action is sent to a store,
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/// a reducer is run on the current state, and this process cannot be done from multiple threads.
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/// It is possible to make this process thread-safe by introducing locks or queues, but this
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/// introduces new complications:
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///
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/// * If done simply with `DispatchQueue.main.async` you will incur a thread hop even when you are
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/// already on the main thread. This can lead to unexpected behavior in UIKit and SwiftUI, where
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/// sometimes you are required to do work synchronously, such as in animation blocks.
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///
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/// * It is possible to create a scheduler that performs its work immediately when on the main
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/// thread and otherwise uses `DispatchQueue.main.async` (_e.g._, see Combine Schedulers'
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/// [UIScheduler][uischeduler]).
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///
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/// This introduces a lot more complexity, and should probably not be adopted without having a very
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/// good reason.
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///
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/// This is why we require all actions be sent from the same thread. This requirement is in the same
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/// spirit of how `URLSession` and other Apple APIs are designed. Those APIs tend to deliver their
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/// outputs on whatever thread is most convenient for them, and then it is your responsibility to
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/// dispatch back to the main queue if that's what you need. The Composable Architecture makes you
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/// responsible for making sure to send actions on the main thread. If you are using an effect that
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/// may deliver its output on a non-main thread, you must explicitly perform `.receive(on:)` in
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/// order to force it back on the main thread.
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///
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/// This approach makes the fewest number of assumptions about how effects are created and
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/// transformed, and prevents unnecessary thread hops and re-dispatching. It also provides some
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/// testing benefits. If your effects are not responsible for their own scheduling, then in tests
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/// all of the effects would run synchronously and immediately. You would not be able to test how
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/// multiple in-flight effects interleave with each other and affect the state of your application.
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/// However, by leaving scheduling out of the ``Store`` we get to test these aspects of our effects
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/// if we so desire, or we can ignore if we prefer. We have that flexibility.
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///
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/// [uischeduler]: https://github.com/pointfreeco/combine-schedulers/blob/main/Sources/CombineSchedulers/UIScheduler.swift
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///
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/// #### Thread safety checks
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///
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/// The store performs some basic thread safety checks in order to help catch mistakes. Stores
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/// constructed via the initializer ``init(initialState:reducer:prepareDependencies:)`` are assumed
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/// to run only on the main thread, and so a check is executed immediately to make sure that is the
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/// case. Further, all actions sent to the store and all scopes (see ``scope(state:action:)-9iai9``) of
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/// the store are also checked to make sure that work is performed on the main thread.
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public final class Store<State, Action> {
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private var bufferedActions: [Action] = []
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@_spi(Internals) public var effectCancellables: [UUID: AnyCancellable] = [:]
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var _isInvalidated = { false }
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private var isSending = false
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var parentCancellable: AnyCancellable?
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private let reducer: any ReducerProtocol<State, Action>
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@_spi(Internals) public var state: CurrentValueSubject<State, Never>
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#if DEBUG
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private let mainThreadChecksEnabled: Bool
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#endif
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/// Initializes a store from an initial state and a reducer.
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///
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/// - Parameters:
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/// - initialState: The state to start the application in.
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/// - reducer: The reducer that powers the business logic of the application.
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/// - prepareDependencies: A closure that can be used to override dependencies that will be accessed
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/// by the reducer.
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public convenience init<R: ReducerProtocol>(
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initialState: @autoclosure () -> R.State,
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@ReducerBuilder<State, Action> reducer: () -> R,
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withDependencies prepareDependencies: ((inout DependencyValues) -> Void)? = nil
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) where R.State == State, R.Action == Action {
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if let prepareDependencies = prepareDependencies {
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let (initialState, reducer) = withDependencies(prepareDependencies) {
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(initialState(), reducer())
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}
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self.init(
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initialState: initialState,
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reducer: reducer.transformDependency(\.self, transform: prepareDependencies),
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mainThreadChecksEnabled: true
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)
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} else {
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self.init(
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initialState: initialState(),
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reducer: reducer(),
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mainThreadChecksEnabled: true
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)
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}
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}
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/// Calls the given closure with the current state of the store.
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///
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/// A lightweight way of accessing store state when no view store is available and state does not
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/// need to be observed, _e.g._ by a SwiftUI view. If a view store is available, prefer
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/// ``ViewStore/state-swift.property``.
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///
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/// - Parameter body: A closure that takes the current state of the store as its sole argument. If
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/// the closure has a return value, that value is also used as the return value of the
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/// `withState` method. The state argument reflects the current state of the store only for the
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/// duration of the closure's execution, and is not observable over time, _e.g._ by SwiftUI. If
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/// you want to observe store state in a view, use a ``ViewStore`` instead.
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/// - Returns: The return value, if any, of the `body` closure.
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public func withState<R>(_ body: (State) -> R) -> R {
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body(self.state.value)
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}
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/// Sends an action to the store.
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///
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/// A lightweight way to send actions to the store when no view store is available. If a view
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/// store is available, prefer ``ViewStore/send(_:)``.
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///
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/// - Parameter action: An action.
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public func send(_ action: Action) {
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_ = self.send(action, originatingFrom: nil)
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}
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/// Scopes the store to one that exposes child state and actions.
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///
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/// This can be useful for deriving new stores to hand to child views in an application. For
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/// example:
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///
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/// ```swift
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/// // Application state made from child states.
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/// struct AppFeature: ReducerProtocol {
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/// struct State {
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/// var login: Login.State
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/// // ...
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/// }
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/// enum Action {
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/// case login(Login.Action)
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/// // ...
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/// }
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///
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/// // A store that runs the entire application.
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/// let store = Store(initialState: AppFeature.State()) {
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/// AppFeature()
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/// }
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///
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/// // Construct a login view by scoping the store
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/// // to one that works with only login domain.
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/// LoginView(
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/// store: store.scope(
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/// state: \.login,
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/// action: AppFeature.Action.login
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/// )
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/// )
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/// ```
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///
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/// Scoping in this fashion allows you to better modularize your application. In this case,
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/// `LoginView` could be extracted to a module that has no access to `AppFeature.State` or
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/// `AppFeature.Action`.
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///
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/// Scoping also gives a view the opportunity to focus on just the state and actions it cares
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/// about, even if its feature domain is larger.
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///
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/// For example, the above login domain could model a two screen login flow: a login form followed
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/// by a two-factor authentication screen. The second screen's domain might be nested in the
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/// first:
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///
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/// ```swift
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/// struct Login: ReducerProtocol {
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/// struct State: Equatable {
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/// var email = ""
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/// var password = ""
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/// var twoFactorAuth: TwoFactorAuthState?
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/// }
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/// enum Action: Equatable {
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/// case emailChanged(String)
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/// case loginButtonTapped
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/// case loginResponse(Result<TwoFactorAuthState, LoginError>)
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/// case passwordChanged(String)
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/// case twoFactorAuth(TwoFactorAuthAction)
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/// }
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/// // ...
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/// }
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/// ```
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///
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/// The login view holds onto a store of this domain:
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///
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/// ```swift
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/// struct LoginView: View {
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/// let store: StoreOf<Login>
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///
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/// var body: some View { /* ... */ }
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/// }
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/// ```
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///
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/// If its body were to use a view store of the same domain, this would introduce a number of
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/// problems:
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///
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/// * The login view would be able to read from `twoFactorAuth` state. This state is only intended
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/// to be read from the two-factor auth screen.
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///
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/// * Even worse, changes to `twoFactorAuth` state would now cause SwiftUI to recompute
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/// `LoginView`'s body unnecessarily.
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///
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/// * The login view would be able to send `twoFactorAuth` actions. These actions are only
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/// intended to be sent from the two-factor auth screen (and reducer).
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///
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/// * The login view would be able to send non user-facing login actions, like `loginResponse`.
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/// These actions are only intended to be used in the login reducer to feed the results of
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/// effects back into the store.
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///
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/// To avoid these issues, one can introduce a view-specific domain that slices off the subset of
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/// state and actions that a view cares about:
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///
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/// ```swift
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/// extension LoginView {
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/// struct ViewState: Equatable {
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/// var email: String
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/// var password: String
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/// }
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///
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/// enum ViewAction: Equatable {
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/// case emailChanged(String)
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/// case loginButtonTapped
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/// case passwordChanged(String)
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/// }
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/// }
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/// ```
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///
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/// One can also introduce a couple helpers that transform feature state into view state and
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/// transform view actions into feature actions.
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///
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/// ```swift
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/// extension Login.State {
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/// var view: LoginView.ViewState {
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/// .init(email: self.email, password: self.password)
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/// }
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/// }
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///
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/// extension LoginView.ViewAction {
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/// var feature: Login.Action {
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/// switch self {
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/// case let .emailChanged(email)
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/// return .emailChanged(email)
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/// case .loginButtonTapped:
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/// return .loginButtonTapped
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/// case let .passwordChanged(password)
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/// return .passwordChanged(password)
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/// }
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/// }
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/// }
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/// ```
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///
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/// With these helpers defined, `LoginView` can now scope its store's feature domain into its view
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/// domain:
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///
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/// ```swift
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/// var body: some View {
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/// WithViewStore(
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/// self.store, observe: \.view, send: \.feature
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/// ) { viewStore in
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/// // ...
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/// }
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/// }
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/// ```
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///
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/// This view store is now incapable of reading any state but view state (and will not recompute
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/// when non-view state changes), and is incapable of sending any actions but view actions.
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///
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/// - Parameters:
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/// - toChildState: A function that transforms `State` into `ChildState`.
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/// - fromChildAction: A function that transforms `ChildAction` into `Action`.
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/// - Returns: A new store with its domain (state and action) transformed.
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public func scope<ChildState, ChildAction>(
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state toChildState: @escaping (State) -> ChildState,
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action fromChildAction: @escaping (ChildAction) -> Action
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) -> Store<ChildState, ChildAction> {
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self.scope(state: toChildState, action: fromChildAction, removeDuplicates: nil)
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}
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/// Scopes the store to one that exposes child state and actions.
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///
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/// This is a special overload of ``scope(state:action:)-9iai9`` that works specifically for
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/// ``PresentationState`` and ``PresentationAction``.
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///
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/// - Parameters:
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/// - toChildState: A function that transforms `State` into ``PresentationState``.
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/// - fromChildAction: A function that transforms ``PresentationAction`` into `Action`.
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/// - Returns: A new store with its domain (state and action) transformed.
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public func scope<ChildState, ChildAction>(
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state toChildState: @escaping (State) -> PresentationState<ChildState>,
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action fromChildAction: @escaping (PresentationAction<ChildAction>) -> Action
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) -> Store<PresentationState<ChildState>, PresentationAction<ChildAction>> {
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self.scope(
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state: toChildState,
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action: fromChildAction,
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removeDuplicates: {
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$0.sharesStorage(with: $1)
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}
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)
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}
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func scope<ChildState, ChildAction>(
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state toChildState: @escaping (State) -> ChildState,
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action fromChildAction: @escaping (ChildAction) -> Action,
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removeDuplicates isDuplicate: ((ChildState, ChildState) -> Bool)?
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) -> Store<ChildState, ChildAction> {
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self.threadCheck(status: .scope)
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return self.reducer.rescope(
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self,
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state: toChildState,
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action: { fromChildAction($1) },
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removeDuplicates: isDuplicate
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)
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}
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func invalidate(_ isInvalid: @escaping (State) -> Bool) -> Store {
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self.threadCheck(status: .scope)
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let store: Store = self.reducer.rescope(
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self,
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state: { $0 },
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action: { state, action in isInvalid(state) && BindingLocal.isActive ? nil : action },
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removeDuplicates: { isInvalid($0) && isInvalid($1) }
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)
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store._isInvalidated = { self._isInvalidated() || isInvalid(self.state.value) }
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return store
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}
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@_spi(Internals)
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public func send(
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_ action: Action,
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originatingFrom originatingAction: Action?
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) -> Task<Void, Never>? {
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self.threadCheck(status: .send(action, originatingAction: originatingAction))
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self.bufferedActions.append(action)
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guard !self.isSending else { return nil }
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self.isSending = true
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var currentState = self.state.value
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let tasks = Box<[Task<Void, Never>]>(wrappedValue: [])
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defer {
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withExtendedLifetime(self.bufferedActions) {
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self.bufferedActions.removeAll()
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}
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self.state.value = currentState
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self.isSending = false
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if !self.bufferedActions.isEmpty {
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if let task = self.send(
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self.bufferedActions.removeLast(), originatingFrom: originatingAction
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) {
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tasks.wrappedValue.append(task)
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}
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}
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}
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var index = self.bufferedActions.startIndex
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while index < self.bufferedActions.endIndex {
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defer { index += 1 }
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let action = self.bufferedActions[index]
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let effect = self.reducer.reduce(into: ¤tState, action: action)
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switch effect.operation {
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case .none:
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break
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case let .publisher(publisher):
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var didComplete = false
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let boxedTask = Box<Task<Void, Never>?>(wrappedValue: nil)
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let uuid = UUID()
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let effectCancellable = withEscapedDependencies { continuation in
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publisher
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.handleEvents(
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receiveCancel: { [weak self] in
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self?.threadCheck(status: .effectCompletion(action))
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self?.effectCancellables[uuid] = nil
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}
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)
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.sink(
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receiveCompletion: { [weak self] _ in
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self?.threadCheck(status: .effectCompletion(action))
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boxedTask.wrappedValue?.cancel()
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didComplete = true
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self?.effectCancellables[uuid] = nil
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},
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receiveValue: { [weak self] effectAction in
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guard let self = self else { return }
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if let task = continuation.yield({
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self.send(effectAction, originatingFrom: action)
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}) {
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tasks.wrappedValue.append(task)
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}
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}
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)
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}
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if !didComplete {
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let task = Task<Void, Never> { @MainActor in
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for await _ in AsyncStream<Void>.never {}
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effectCancellable.cancel()
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}
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boxedTask.wrappedValue = task
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tasks.wrappedValue.append(task)
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self.effectCancellables[uuid] = effectCancellable
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}
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case let .run(priority, operation):
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withEscapedDependencies { continuation in
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tasks.wrappedValue.append(
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Task(priority: priority) { @MainActor in
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#if DEBUG
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let isCompleted = LockIsolated(false)
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defer { isCompleted.setValue(true) }
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#endif
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await operation(
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Send { effectAction in
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#if DEBUG
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if isCompleted.value {
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runtimeWarn(
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"""
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An action was sent from a completed effect:
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Action:
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\(debugCaseOutput(effectAction))
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Effect returned from:
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\(debugCaseOutput(action))
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|
|
Avoid sending actions using the 'send' argument from 'EffectTask.run' after \
|
|
the effect has completed. This can happen if you escape the 'send' argument in \
|
|
an unstructured context.
|
|
|
|
To fix this, make sure that your 'run' closure does not return until you're \
|
|
done calling 'send'.
|
|
"""
|
|
)
|
|
}
|
|
#endif
|
|
if let task = continuation.yield({
|
|
self.send(effectAction, originatingFrom: action)
|
|
}) {
|
|
tasks.wrappedValue.append(task)
|
|
}
|
|
}
|
|
)
|
|
}
|
|
)
|
|
}
|
|
}
|
|
}
|
|
|
|
guard !tasks.wrappedValue.isEmpty else { return nil }
|
|
return Task {
|
|
await withTaskCancellationHandler {
|
|
var index = tasks.wrappedValue.startIndex
|
|
while index < tasks.wrappedValue.endIndex {
|
|
defer { index += 1 }
|
|
await tasks.wrappedValue[index].value
|
|
}
|
|
} onCancel: {
|
|
var index = tasks.wrappedValue.startIndex
|
|
while index < tasks.wrappedValue.endIndex {
|
|
defer { index += 1 }
|
|
tasks.wrappedValue[index].cancel()
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Returns a "stateless" store by erasing state to `Void`.
|
|
public var stateless: Store<Void, Action> {
|
|
self.scope(state: { _ in () }, action: { $0 })
|
|
}
|
|
|
|
/// Returns an "actionless" store by erasing action to `Never`.
|
|
public var actionless: Store<State, Never> {
|
|
func absurd<A>(_ never: Never) -> A {}
|
|
return self.scope(state: { $0 }, action: absurd)
|
|
}
|
|
|
|
private enum ThreadCheckStatus {
|
|
case effectCompletion(Action)
|
|
case `init`
|
|
case scope
|
|
case send(Action, originatingAction: Action?)
|
|
}
|
|
|
|
@inline(__always)
|
|
private func threadCheck(status: ThreadCheckStatus) {
|
|
#if DEBUG
|
|
guard self.mainThreadChecksEnabled && !Thread.isMainThread
|
|
else { return }
|
|
|
|
switch status {
|
|
case let .effectCompletion(action):
|
|
runtimeWarn(
|
|
"""
|
|
An effect completed on a non-main thread. …
|
|
|
|
Effect returned from:
|
|
\(debugCaseOutput(action))
|
|
|
|
Make sure to use ".receive(on:)" on any effects that execute on background threads to \
|
|
receive their output on the main thread.
|
|
|
|
The "Store" class is not thread-safe, and so all interactions with an instance of \
|
|
"Store" (including all of its scopes and derived view stores) must be done on the main \
|
|
thread.
|
|
"""
|
|
)
|
|
|
|
case .`init`:
|
|
runtimeWarn(
|
|
"""
|
|
A store initialized on a non-main thread. …
|
|
|
|
The "Store" class is not thread-safe, and so all interactions with an instance of \
|
|
"Store" (including all of its scopes and derived view stores) must be done on the main \
|
|
thread.
|
|
"""
|
|
)
|
|
|
|
case .scope:
|
|
runtimeWarn(
|
|
"""
|
|
"Store.scope" was called on a non-main thread. …
|
|
|
|
The "Store" class is not thread-safe, and so all interactions with an instance of \
|
|
"Store" (including all of its scopes and derived view stores) must be done on the main \
|
|
thread.
|
|
"""
|
|
)
|
|
|
|
case let .send(action, originatingAction: nil):
|
|
runtimeWarn(
|
|
"""
|
|
"ViewStore.send" was called on a non-main thread with: \(debugCaseOutput(action)) …
|
|
|
|
The "Store" class is not thread-safe, and so all interactions with an instance of \
|
|
"Store" (including all of its scopes and derived view stores) must be done on the main \
|
|
thread.
|
|
"""
|
|
)
|
|
|
|
case let .send(action, originatingAction: .some(originatingAction)):
|
|
runtimeWarn(
|
|
"""
|
|
An effect published an action on a non-main thread. …
|
|
|
|
Effect published:
|
|
\(debugCaseOutput(action))
|
|
|
|
Effect returned from:
|
|
\(debugCaseOutput(originatingAction))
|
|
|
|
Make sure to use ".receive(on:)" on any effects that execute on background threads to \
|
|
receive their output on the main thread.
|
|
|
|
The "Store" class is not thread-safe, and so all interactions with an instance of \
|
|
"Store" (including all of its scopes and derived view stores) must be done on the main \
|
|
thread.
|
|
"""
|
|
)
|
|
}
|
|
#endif
|
|
}
|
|
|
|
init<R: ReducerProtocol>(
|
|
initialState: R.State,
|
|
reducer: R,
|
|
mainThreadChecksEnabled: Bool
|
|
) where R.State == State, R.Action == Action {
|
|
self.state = CurrentValueSubject(initialState)
|
|
self.reducer = reducer
|
|
#if DEBUG
|
|
self.mainThreadChecksEnabled = mainThreadChecksEnabled
|
|
#endif
|
|
self.threadCheck(status: .`init`)
|
|
}
|
|
}
|
|
|
|
/// A convenience type alias for referring to a store of a given reducer's domain.
|
|
///
|
|
/// Instead of specifying two generics:
|
|
///
|
|
/// ```swift
|
|
/// let store: Store<Feature.State, Feature.Action>
|
|
/// ```
|
|
///
|
|
/// You can specify a single generic:
|
|
///
|
|
/// ```swift
|
|
/// let store: StoreOf<Feature>
|
|
/// ```
|
|
public typealias StoreOf<R: ReducerProtocol> = Store<R.State, R.Action>
|
|
|
|
extension ReducerProtocol {
|
|
fileprivate func rescope<ChildState, ChildAction>(
|
|
_ store: Store<State, Action>,
|
|
state toChildState: @escaping (State) -> ChildState,
|
|
action fromChildAction: @escaping (ChildState, ChildAction) -> Action?,
|
|
removeDuplicates isDuplicate: ((ChildState, ChildState) -> Bool)?
|
|
) -> Store<ChildState, ChildAction> {
|
|
(self as? any AnyScopedReducer ?? ScopedReducer(rootStore: store)).rescope(
|
|
store,
|
|
state: toChildState,
|
|
action: fromChildAction,
|
|
removeDuplicates: isDuplicate
|
|
)
|
|
}
|
|
}
|
|
|
|
private final class ScopedReducer<
|
|
RootState, RootAction, State, Action
|
|
>: ReducerProtocol {
|
|
let rootStore: Store<RootState, RootAction>
|
|
let toScopedState: (RootState) -> State
|
|
private let parentStores: [Any]
|
|
let fromScopedAction: (State, Action) -> RootAction?
|
|
private(set) var isSending = false
|
|
|
|
@inlinable
|
|
init(rootStore: Store<RootState, RootAction>)
|
|
where RootState == State, RootAction == Action {
|
|
self.rootStore = rootStore
|
|
self.toScopedState = { $0 }
|
|
self.parentStores = []
|
|
self.fromScopedAction = { $1 }
|
|
}
|
|
|
|
@inlinable
|
|
init(
|
|
rootStore: Store<RootState, RootAction>,
|
|
state toScopedState: @escaping (RootState) -> State,
|
|
action fromScopedAction: @escaping (State, Action) -> RootAction?,
|
|
parentStores: [Any]
|
|
) {
|
|
self.rootStore = rootStore
|
|
self.toScopedState = toScopedState
|
|
self.fromScopedAction = fromScopedAction
|
|
self.parentStores = parentStores
|
|
}
|
|
|
|
@inlinable
|
|
func reduce(
|
|
into state: inout State, action: Action
|
|
) -> EffectTask<Action> {
|
|
self.isSending = true
|
|
defer {
|
|
state = self.toScopedState(self.rootStore.state.value)
|
|
self.isSending = false
|
|
}
|
|
if let action = self.fromScopedAction(state, action),
|
|
let task = self.rootStore.send(action, originatingFrom: nil)
|
|
{
|
|
return .run { _ in await task.cancellableValue }
|
|
} else {
|
|
return .none
|
|
}
|
|
}
|
|
}
|
|
|
|
protocol AnyScopedReducer {
|
|
func rescope<ScopedState, ScopedAction, RescopedState, RescopedAction>(
|
|
_ store: Store<ScopedState, ScopedAction>,
|
|
state toRescopedState: @escaping (ScopedState) -> RescopedState,
|
|
action fromRescopedAction: @escaping (RescopedState, RescopedAction) -> ScopedAction?,
|
|
removeDuplicates isDuplicate: ((RescopedState, RescopedState) -> Bool)?
|
|
) -> Store<RescopedState, RescopedAction>
|
|
}
|
|
|
|
extension ScopedReducer: AnyScopedReducer {
|
|
@inlinable
|
|
func rescope<ScopedState, ScopedAction, RescopedState, RescopedAction>(
|
|
_ store: Store<ScopedState, ScopedAction>,
|
|
state toRescopedState: @escaping (ScopedState) -> RescopedState,
|
|
action fromRescopedAction: @escaping (RescopedState, RescopedAction) -> ScopedAction?,
|
|
removeDuplicates isDuplicate: ((RescopedState, RescopedState) -> Bool)?
|
|
) -> Store<RescopedState, RescopedAction> {
|
|
let fromScopedAction = self.fromScopedAction as! (ScopedState, ScopedAction) -> RootAction?
|
|
let reducer = ScopedReducer<RootState, RootAction, RescopedState, RescopedAction>(
|
|
rootStore: self.rootStore,
|
|
state: { _ in toRescopedState(store.state.value) },
|
|
action: { fromRescopedAction($0, $1).flatMap { fromScopedAction(store.state.value, $0) } },
|
|
parentStores: self.parentStores + [store]
|
|
)
|
|
let childStore = Store<RescopedState, RescopedAction>(
|
|
initialState: toRescopedState(store.state.value),
|
|
reducer: reducer
|
|
)
|
|
childStore._isInvalidated = store._isInvalidated
|
|
childStore.parentCancellable = store.state
|
|
.dropFirst()
|
|
.sink { [weak childStore] newValue in
|
|
guard !reducer.isSending, let childStore = childStore else { return }
|
|
let newValue = toRescopedState(newValue)
|
|
guard isDuplicate.map({ !$0(childStore.state.value, newValue) }) ?? true else {
|
|
return
|
|
}
|
|
childStore.state.value = newValue
|
|
}
|
|
return childStore
|
|
}
|
|
}
|