Subscriptions addition to Combine

Subscriptions.swift

//
//  Combine+Extensions.swift
//  Common
//
//  Created by Michael Long on 8/27/22.
//

import Foundation
import Combine

typealias Subscriptions = Set<AnyCancellable>

extension Subscriptions {

    public mutating func add(_ subscriptions: AnyCancellable...) {
        subscriptions.forEach { self.insert($0) }
    }

    public mutating func add(@SubscriptionBuilder builder: () -> [AnyCancellable]) {
        builder().forEach { self.insert($0) }
    }

    public mutating func add<SuccessType: Sendable, FailureType: Error>(_ task: Task<SuccessType, FailureType>) {
        add(AnyCancellable(task.cancel))
    }

    public mutating func cancel() {
        self = []
    }

#if swift(>=5.4)
    @resultBuilder
    public struct SubscriptionBuilder {
        public static func buildBlock(_ subscriptions: AnyCancellable...) -> [AnyCancellable] {
            return subscriptions
        }
    }
#else
    @_functionBuilder
    public struct SubscriptionBuilder {
        public static func buildBlock(_ subscriptions: AnyCancellable...) -> [AnyCancellable] {
            return subscriptions
        }
    }
#endif

}

extension Task where Success == Sendable, Failure == Error {
    func store(in container: inout Subscriptions) {
        container.add(self)
    }
}

func test() {
    let publisher1 = CurrentValueSubject<String, Never>("Hello")
    let publisher2 = CurrentValueSubject<String, Never>("World")

    var subscriptions = Subscriptions()

    // variadic
    subscriptions.add(
        publisher1.sink { string in
            print(string)
        },
        publisher2.sink { string in
            print(string)
        }
    )

    // result builder
    subscriptions.add {
        publisher1.sink { string in
            print(string)
        }
        publisher2.sink { string in
            print(string)
        }
    }
    
    subscriptions.cancel()
}