dispatch_async and block in iOS

Question

What this piece of code mean?

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        TMBaseParser *parser=[[TMBaseParser al         


        

Answer 1

If the above code snippets doesn't work then, try this:

Objective-C:

dispatch_async(dispatch_get_main_queue(), ^{

});

UI updates should always be executed from the main queue. The "^" symbol indicates a start of a block.

Swift 3:

DispatchQueue.global(qos: .background).async {
    print("This is run on the background queue")

    DispatchQueue.main.async {
        print("This is run on the main queue, after the previous code in outer block")
    }
}