Is there any way of locking an object in Swift like in C#

Question

I have the following code:

func foo() {
    var sum = 0
    var pendingElements = 10

    for i in 0 ..< 10 {
        proccessElementAsync(i) { value in
          


        

Answer 1

Hope this will help you.

func lock(obj: AnyObject, blk:() -> ()) {
    objc_sync_enter(obj)
    blk()
    objc_sync_exit(obj)
}

var pendingElements = 10

func foo() {
    var sum = 0
    var pendingElements = 10

    for i in 0 ..< 10 {
        proccessElementAsync(i) { value in

            lock(pendingElements) {
                sum += value
                pendingElements--

                if pendingElements == 0 {
                    println(sum)
                }
            }

        }
    }
}

Answer 2

There is no native locking tools, but there are workarounds like explained in this SO question:

What is the Swift equivalent to Objective-C's "@synchronized"?

Using one of the answers, you can create a function:

    func synchronize(lockObj: AnyObject!, closure: ()->()){
        objc_sync_enter(lockObj)
        closure()
        objc_sync_exit(lockObj)
    }

and then:

     func foo() {
        var sum = 0
        var pendingElements = 10

        for i in 0 ..< 10 {
            processElementAsync(i) { value in

                synchronize(pendingElements) {
                    sum += value
                    pendingElements--

                    if pendingElements == 0 {
                        println(sum)
                    }
                }

            }
        }
    }