Swift - Grand Central Dispatch vs Blocks/Closures

Question

I'm trying to write an HTTP request using Swift and I really only see people going one way or another (actually not so much GCD) to do HTTP requests on iOS.

If I want to make an HTTP request in iOS, what would be the best way to go about it: Use Grand Central Dispatch or write some closure block? Also, where can I find some great examples. From what I read online, I'm having a hard time seeing the benefits of one over the other.

At the moment, I have this code:

    let priority = DISPATCH_QUEUE_PRIORITY_DEFAULT

    dispatch_async(dispatch_get_global_queue(priority, 0), { ()->() in

        self.activityIndicator.startAnimating()
        self.authenticateUser()

        dispatch_async(dispatch_get_main_queue(), {
            self.activityIndicator.stopAnimating()
        })
    })

From what I see in the Debug Session tab for the Processor, I can see it jump from Thread X to Thread Y (for authenticateUser) and back to Thread X. Which is good - this is what I want (I'm sure).

Any good examples of GCD or Blocks/Closures written in Swift that you might be aware of would be very handy too. Thanks!

GCD uses closures. You can't use GCD in Swift without using closures. Anyway, have you looked at the URL Loading System Programming Guide? — rob mayoff
Take a look: medium.com/swift-programming/http-in-swift-693b3a7bf086. — Maxim Shoustin
@MaximShoustin is this better than using GCD or a more "Correct Way" of doing async http requests? — Mario A Guzman
Using blocks + dispatch_async VS. NSURLSession: teamtreehouse.com/forum/…. For ios7+ i would use NSURLSession. For backwards compatibility - GCD — Maxim Shoustin

Alberto Barrera Alberto Barrera · Accepted Answer · 2014-09-25T21:35:11

Use NSURLSession to make your HTTP request. Use GCD to implement concurrency in your app (multiple things happening at the same time). And use Closures to give a structure to your application. As you can see now, all of them can be used at the same time.

By the way, always remember this: All UI modifications must be called in the main thread, in your code you are calling this self.activityIndicator.startAnimating() on a concurrent queue.

Swift - Grand Central Dispatch vs Blocks/Closures

2 Answers