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| 1 | +// |
| 2 | +// ConcurrentOperation.swift |
| 3 | +// NetworkingInOperations-Example |
| 4 | +// |
| 5 | +// Created by William Boles on 11/07/2018. |
| 6 | +// Copyright © 2018 Boles. All rights reserved. |
| 7 | +// |
| 8 | + |
| 9 | +import Foundation |
| 10 | + |
| 11 | +enum ConcurrentOperationError: Error, Equatable { |
| 12 | + case cancelled |
| 13 | +} |
| 14 | + |
| 15 | +class ConcurrentOperation<Value>: Operation, @unchecked Sendable { |
| 16 | + private(set) var completionHandler: ((_ result: Result<Value, Error>) -> Void)? |
| 17 | + |
| 18 | + private let lock = NSRecursiveLock() |
| 19 | + |
| 20 | + // MARK: - Init |
| 21 | + |
| 22 | + init(completionHandler: @escaping (_ result: Result<Value, Error>) -> Void) { |
| 23 | + self.completionHandler = completionHandler |
| 24 | + |
| 25 | + super.init() |
| 26 | + } |
| 27 | + |
| 28 | + // MARK: - State |
| 29 | + |
| 30 | + private enum State: String { |
| 31 | + case ready = "isReady" |
| 32 | + case executing = "isExecuting" |
| 33 | + case finished = "isFinished" |
| 34 | + } |
| 35 | + |
| 36 | + private var _state = State.ready { |
| 37 | + willSet { |
| 38 | + willChangeValue(forKey: _state.rawValue) |
| 39 | + willChangeValue(forKey: newValue.rawValue) |
| 40 | + } |
| 41 | + didSet { |
| 42 | + didChangeValue(forKey: _state.rawValue) |
| 43 | + didChangeValue(forKey: oldValue.rawValue) |
| 44 | + } |
| 45 | + } |
| 46 | + |
| 47 | + private var state: State { |
| 48 | + get { |
| 49 | + lock.lock() |
| 50 | + defer { lock.unlock() } |
| 51 | + |
| 52 | + return _state |
| 53 | + } |
| 54 | + set { |
| 55 | + lock.lock() |
| 56 | + defer { lock.unlock() } |
| 57 | + |
| 58 | + _state = newValue |
| 59 | + } |
| 60 | + } |
| 61 | + |
| 62 | + override var isReady: Bool { |
| 63 | + return super.isReady && state == .ready |
| 64 | + } |
| 65 | + |
| 66 | + override var isExecuting: Bool { |
| 67 | + return state == .executing |
| 68 | + } |
| 69 | + |
| 70 | + override var isFinished: Bool { |
| 71 | + return state == .finished |
| 72 | + } |
| 73 | + |
| 74 | + override var isAsynchronous: Bool { |
| 75 | + return true |
| 76 | + } |
| 77 | + |
| 78 | + // MARK: - Lifecycle |
| 79 | + |
| 80 | + override func start() { |
| 81 | + guard !isCancelled else { |
| 82 | + finish(result: .failure(ConcurrentOperationError.cancelled)) |
| 83 | + return |
| 84 | + } |
| 85 | + |
| 86 | + state = .executing |
| 87 | + |
| 88 | + main() |
| 89 | + } |
| 90 | + |
| 91 | + func finish(result: Result<Value, Error>) { |
| 92 | + lock.lock() |
| 93 | + defer { lock.unlock() } |
| 94 | + |
| 95 | + guard !isFinished else { |
| 96 | + return |
| 97 | + } |
| 98 | + |
| 99 | + state = .finished |
| 100 | + |
| 101 | + completionHandler?(result) |
| 102 | + } |
| 103 | + |
| 104 | + override func cancel() { |
| 105 | + super.cancel() |
| 106 | + |
| 107 | + finish(result: .failure(ConcurrentOperationError.cancelled)) |
| 108 | + } |
| 109 | +} |
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