leesen11 / learningcombine Goto Github PK

final public class Future<Output, Failure> : Publisher where Failure: Error { 
    public typealias Promise = (Result<Output, Failure>) -> Void 
    ...
}

public protocol Publisher {
    // publisher生成的值的类型
    associatedtype Output
    // publisher课程产生的错误类型，如果是Never的话，表明这个publisher永远不会生成错误
    associatedtype Failure: Error
 
    // 订阅者通过调用publisher的subscribe(_:)方法来将二者绑定在一起
    func receive<S>(subscriber: S) where S: Subscriber, Self.Failure == S.Failure, Self.Output == S.Input
}

extension Publisher {
    // subscribe(_:)的实现会调用receive(_:)以此来将subscriber和publisher进行关联，也就是创建一个订阅关系
    public func subscribe<S>(_ subscriber: S) where S: Subscriber, Self.Failure == S.Failure, Self.Output == S.Input
}

public protocol Subscriber: CustomCombineIdentifierConvertible {
    // subscriber接收的值类型
    associatedtype Input
    // subscriber接收的错误类型，如果subscriber不接收任何错误的话，那么使用Never
    associatedtype Failure: Error

    // publisher通过调用subscriber的receive(subscription:)方法来将subscription传递给subscriber
    func receive(subscription: Subscription)

    // publisher调用subscriber的receive(_:)来将它刚刚生成的新值发送给subscriber
    func receive(_ input: Self.Input) -> Subscribers.Demand

    // publisher停止发送数据或者因为错误终止时，会调用subscriber的receive(completion:)告诉subscriber
    func receive(completion: Subscribers.Completion<Self.Failure>)
}

public protocol Subscription: Cancellable, CustomCombineIdentifierConvertible {
    // subscriber会调用request(_:)时指定的最大数量或无限制，来表明它是否愿意接受更多的数据
    func request(_ demand: Subscribers.Demand)
}