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sharplet/Always.swift

Last active February 15, 2024 18:50
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  1. sharplet revised this gist May 22, 2020. 1 changed file with 23 additions and 1 deletion.
    24 changes: 23 additions & 1 deletion Always.swift
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    // Copyright (c) 2019–20 Adam Sharp and thoughtbot, inc.
    //
    // Permission is hereby granted, free of charge, to any person obtaining a copy
    // of this software and associated documentation files (the "Software"), to deal
    // in the Software without restriction, including without limitation the rights
    // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    // copies of the Software, and to permit persons to whom the Software is
    // furnished to do so, subject to the following conditions:
    //
    // The above copyright notice and this permission notice shall be included in
    // all copies or substantial portions of the Software.
    //
    // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    // THE SOFTWARE.

    import Combine

    /// A publisher that repeatedly sends the same value as long as there
    /// is demand.
    public struct Always<Output>: Publisher {
    public typealias Failure = Never

    private var output: Output
    public let output: Output

    public init(_ output: Output) {
    self.output = output
  2. sharplet created this gist May 3, 2020.
    44 changes: 44 additions & 0 deletions Always.swift
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    import Combine

    public struct Always<Output>: Publisher {
    public typealias Failure = Never

    private var output: Output

    public init(_ output: Output) {
    self.output = output
    }

    public func receive<S: Subscriber>(subscriber: S) where S.Input == Output, S.Failure == Failure {
    let subscription = Subscription(output: output, subscriber: subscriber)
    subscriber.receive(subscription: subscription)
    }
    }

    private extension Always {
    final class Subscription<S: Subscriber> where S.Input == Output, S.Failure == Failure {
    private let output: Output
    private var subscriber: S?

    init(output: Output, subscriber: S) {
    self.output = output
    self.subscriber = subscriber
    }
    }
    }

    extension Always.Subscription: Cancellable {
    func cancel() {
    subscriber = nil
    }
    }

    extension Always.Subscription: Subscription {
    func request(_ demand: Subscribers.Demand) {
    var demand = demand
    while let subscriber = subscriber, demand > 0 {
    demand -= 1
    demand += subscriber.receive(output)
    }
    }
    }