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65 lines
2.8 KiB
Swift
65 lines
2.8 KiB
Swift
//===--- PlaygroundDisplay.swift ------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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/// A type that supplies a custom description for playground logging.
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///
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/// Playground logging can generate, at a minimum, a structured description
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/// of any type. If you want to provide a custom description of your type to be
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/// logged in place of the default description, conform to the
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/// `CustomPlaygroundDisplayConvertible` protocol.
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///
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/// Playground logging generates a richer, more specialized description of core
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/// types. For example, the contents of a `String` are logged, as are the
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/// components of an `NSColor` or `UIColor`. The current playground logging
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/// implementation logs specialized descriptions of at least the following
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/// types:
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///
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/// - `String` and `NSString`
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/// - `Int`, `UInt`, and the other standard library integer types
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/// - `Float` and `Double`
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/// - `Bool`
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/// - `Date` and `NSDate`
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/// - `NSAttributedString`
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/// - `NSNumber`
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/// - `NSRange`
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/// - `URL` and `NSURL`
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/// - `CGPoint`, `CGSize`, and `CGRect`
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/// - `NSColor`, `UIColor`, `CGColor`, and `CIColor`
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/// - `NSImage`, `UIImage`, `CGImage`, and `CIImage`
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/// - `NSBezierPath` and `UIBezierPath`
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/// - `NSView` and `UIView`
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///
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/// Playground logging may also be able to support specialized descriptions
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/// of other types.
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///
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/// Conforming to the CustomPlaygroundDisplayConvertible Protocol
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/// -------------------------------------------------------------
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///
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/// To add `CustomPlaygroundDisplayConvertible` conformance to your custom type,
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/// implement the `playgroundDescription` property. If your implementation
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/// returns an instance of one of the types above, that type's specialized
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/// description is used. If you return any other type, a structured description
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/// is generated.
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///
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/// If your type has value semantics, the `playgroundDescription` should be
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/// unaffected by subsequent mutations, if possible.
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///
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/// If your type's `playgroundDescription` returns an instance which itself
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/// conforms to `CustomPlaygroundDisplayConvertible`, then that type's
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/// `playgroundDescription` will be used, and so on. To prevent infinite loops,
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/// playground logging implementations can place a reasonable limit on this
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/// kind of chaining.
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public protocol CustomPlaygroundDisplayConvertible {
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/// A custom playground description for this instance.
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var playgroundDescription: Any { get }
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}
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