116 lines
3.5 KiB
Swift
116 lines
3.5 KiB
Swift
//
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// Copyright (c) 2022 Touch Instinct
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the Software), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED AS IS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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//
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import Foundation
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open class AsyncOperation<Output, Failure: Error>: Operation {
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open var result: Result<Output, Failure>?
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var state: State? = nil { // nil -> isReady == false
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// KVO support
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willSet {
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willChangeValue(forKey: newValue.orReady.rawValue)
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willChangeValue(forKey: state.orReady.rawValue)
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}
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didSet {
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didChangeValue(forKey: state.orReady.rawValue)
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didChangeValue(forKey: oldValue.orReady.rawValue)
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}
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}
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private var dependencyCancelObservations: [NSKeyValueObservation] = []
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// MARK: - Operation override
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open override var isCancelled: Bool {
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state == .isCancelled
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}
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open override var isExecuting: Bool {
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state == .isExecuting
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}
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open override var isFinished: Bool {
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state == .isFinished
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}
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open override var isReady: Bool {
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state == .isReady
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}
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open override var isAsynchronous: Bool {
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true
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}
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open override func start() {
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state = .isExecuting
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if result != nil {
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state = .isFinished
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}
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}
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open override func cancel() {
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state = .isCancelled
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dependencyCancelObservations = []
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}
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// MARK: - Methods for subclass override
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open func handle(result: Result<Output, Failure>) {
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self.result = result
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state = .isFinished
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}
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// MARK: - Completion observation
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public func subscribe(onResult: ((Result<Output, Failure>) -> Void)? = nil) -> NSKeyValueObservation {
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observe(\.isFinished, options: [.new]) { object, change in
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if let isFinished = change.newValue, isFinished {
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if let result = object.result {
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onResult?(result)
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} else {
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assertionFailure("Got nil result from operation but isFinished is true!")
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}
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}
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}
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}
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public func cancelOnCancellation(of dependency: Operation) {
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let cancelObservation = dependency.observe(\.isCancelled) { [weak self] _, change in
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if let isCancelled = change.newValue, isCancelled {
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self?.cancel()
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}
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}
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dependencyCancelObservations.append(cancelObservation)
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}
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}
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private extension Optional where Wrapped == Operation.State {
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var orReady: Wrapped {
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self ?? .isReady
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}
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}
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