Channel Synchronization in Swift

Our example demonstrates how to use channels for synchronization across concurrent operations. Here’s the full source code:

import Foundation

// This is the function we'll run concurrently. The
// `done` channel will be used to notify another
// operation that this function's work is done.
func worker(done: DispatchGroup) {
    print("working...", terminator: "")
    Thread.sleep(forTimeInterval: 1)
    print("done")
    
    // Notify that we're done.
    done.leave()
}

func main() {
    // Create a dispatch group to synchronize operations
    let done = DispatchGroup()
    
    // Start a worker operation, adding it to the dispatch group
    done.enter()
    DispatchQueue.global().async {
        worker(done: done)
    }
    
    // Wait until we receive a notification from the
    // worker on the dispatch group.
    done.wait()
}

main()

To run the program, save it as ChannelSynchronization.swift and use swift to execute it:

$ swift ChannelSynchronization.swift
working...done

In this Swift version, we use DispatchGroup to synchronize operations, which is conceptually similar to channel synchronization in the original example. The DispatchGroup allows us to group multiple operations together and wait for them to complete.

If you removed the done.wait() line from this program, the program would exit before the worker even started or finished its work.

The DispatchQueue.global().async is used to run the worker function concurrently, similar to how goroutines work in the original example.

While Swift doesn’t have built-in channels like some other languages, the combination of Grand Central Dispatch (GCD) and DispatchGroup provides powerful tools for managing concurrency and synchronization in Swift applications.