init

杨锴

2024-08-14 909e20941e45f8712c012db602034b47da0bfdb0

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
//
//  Using.swift
//  RxSwift
//
//  Created by Yury Korolev on 10/15/15.
//  Copyright © 2015 Krunoslav Zaher. All rights reserved.
//
 
extension ObservableType {
    /**
     Constructs an observable sequence that depends on a resource object, whose lifetime is tied to the resulting observable sequence's lifetime.
 
     - seealso: [using operator on reactivex.io](http://reactivex.io/documentation/operators/using.html)
 
     - parameter resourceFactory: Factory function to obtain a resource object.
     - parameter observableFactory: Factory function to obtain an observable sequence that depends on the obtained resource.
     - returns: An observable sequence whose lifetime controls the lifetime of the dependent resource object.
     */
    public static func using<Resource: Disposable>(_ resourceFactory: @escaping () throws -> Resource, observableFactory: @escaping (Resource) throws -> Observable<Element>) -> Observable<Element> {
        Using(resourceFactory: resourceFactory, observableFactory: observableFactory)
    }
}
 
final private class UsingSink<ResourceType: Disposable, Observer: ObserverType>: Sink<Observer>, ObserverType {
    typealias SourceType = Observer.Element 
    typealias Parent = Using<SourceType, ResourceType>
 
    private let parent: Parent
    
    init(parent: Parent, observer: Observer, cancel: Cancelable) {
        self.parent = parent
        super.init(observer: observer, cancel: cancel)
    }
    
    func run() -> Disposable {
        var disposable = Disposables.create()
        
        do {
            let resource = try self.parent.resourceFactory()
            disposable = resource
            let source = try self.parent.observableFactory(resource)
            
            return Disposables.create(
                source.subscribe(self),
                disposable
            )
        } catch let error {
            return Disposables.create(
                Observable.error(error).subscribe(self),
                disposable
            )
        }
    }
    
    func on(_ event: Event<SourceType>) {
        switch event {
        case let .next(value):
            self.forwardOn(.next(value))
        case let .error(error):
            self.forwardOn(.error(error))
            self.dispose()
        case .completed:
            self.forwardOn(.completed)
            self.dispose()
        }
    }
}
 
final private class Using<SourceType, ResourceType: Disposable>: Producer<SourceType> {
    
    typealias Element = SourceType
    
    typealias ResourceFactory = () throws -> ResourceType
    typealias ObservableFactory = (ResourceType) throws -> Observable<SourceType>
    
    fileprivate let resourceFactory: ResourceFactory
    fileprivate let observableFactory: ObservableFactory
    
    
    init(resourceFactory: @escaping ResourceFactory, observableFactory: @escaping ObservableFactory) {
        self.resourceFactory = resourceFactory
        self.observableFactory = observableFactory
    }
    
    override func run<Observer: ObserverType>(_ observer: Observer, cancel: Cancelable) -> (sink: Disposable, subscription: Disposable) where Observer.Element == Element {
        let sink = UsingSink(parent: self, observer: observer, cancel: cancel)
        let subscription = sink.run()
        return (sink: sink, subscription: subscription)
    }
}