ios - Pass value to closure?

Question

I want to do extra logic after last item was processed, but terminal show that i has always the same value as c. Any idea how to pass the loop variable in?

let c = a.count
for var i=0; i<c; i++ {

   dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), {

        // ..

        dispatch_async(dispatch_get_main_queue(), {

            println("i (i) c (c)")
            if i == c-1 {

                // extra stuff would come here
            }
        })
    })
}

Answer 1

By the time your closure is executed, the for loop has already finished and i = c. You need an auxiliary variable inside the for loop:

let c = a.count
for var i=0; i<c; i++ {
    let k = i
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), {

        // ..

        dispatch_async(dispatch_get_main_queue(), {

            println("k (k) c (c)")
            if k == c-1 {

                // extra stuff would come here
            }
        })
    })
}