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dcecad3fe2
* Soft-deprecate `Store.ifLet` We can prefer `observe` and `if let store.scope` now. * wip * wip * Update MigratingTo1.7.md * wip
78 lines
3.1 KiB
Swift
78 lines
3.1 KiB
Swift
import Combine
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extension Store {
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/// Calls one of two closures depending on whether a store's optional state is `nil` or not, and
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/// whenever this condition changes for as long as the cancellable lives.
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///
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/// If the store's state is non-`nil`, it will safely unwrap the value and bundle it into a new
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/// store of non-optional state that is passed to the first closure. If the store's state is
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/// `nil`, the second closure is called instead.
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///
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/// This method is useful for handling navigation in UIKit. The state for a screen the user wants
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/// to navigate to can be held as an optional value in the parent, and when that value goes from
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/// `nil` to non-`nil`, or non-`nil` to `nil`, you can update the navigation stack accordingly:
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///
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/// ```swift
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/// class ParentViewController: UIViewController {
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/// let store: Store<ParentState, ParentAction>
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/// var cancellables: Set<AnyCancellable> = []
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/// // ...
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/// func viewDidLoad() {
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/// // ...
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/// store
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/// .scope(state: \.optionalChild, action: \.child)
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/// .ifLet(
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/// then: { [weak self] childStore in
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/// self?.navigationController?.pushViewController(
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/// ChildViewController(store: childStore),
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/// animated: true
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/// )
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/// },
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/// else: { [weak self] in
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/// guard let self else { return }
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/// navigationController?.popToViewController(self, animated: true)
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/// }
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/// )
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/// .store(in: &cancellables)
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/// }
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/// }
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/// ```
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///
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/// - Parameters:
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/// - unwrap: A function that is called with a store of non-optional state when the store's
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/// state is non-`nil`, or whenever it goes from `nil` to non-`nil`.
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/// - else: A function that is called when the store's optional state is `nil`, or whenever it
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/// goes from non-`nil` to `nil`.
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/// - Returns: A cancellable that maintains a subscription to updates whenever the store's state
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/// goes from `nil` to non-`nil` and vice versa, so that the caller can react to these changes.
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@available(iOS, deprecated: 9999, message: "Use 'observe' and 'if let store.scope', instead.")
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@available(macOS, deprecated: 9999, message: "Use 'observe' and 'if let store.scope', instead.")
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@available(tvOS, deprecated: 9999, message: "Use 'observe' and 'if let store.scope', instead.")
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@available(watchOS, deprecated: 9999, message: "Use 'observe' and 'if let store.scope', instead.")
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public func ifLet<Wrapped>(
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then unwrap: @escaping (_ store: Store<Wrapped, Action>) -> Void,
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else: @escaping () -> Void = {}
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) -> any Cancellable where State == Wrapped? {
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return self
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.publisher
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.removeDuplicates(by: { ($0 != nil) == ($1 != nil) })
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.sink { state in
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if var state = state {
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unwrap(
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self.scope(
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id: self.id(state: \.!, action: \.self),
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state: ToState {
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state = $0 ?? state
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return state
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},
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action: { $0 },
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isInvalid: { $0 == nil }
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)
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)
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} else {
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`else`()
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}
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}
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}
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}
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