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How to run code on the main thread using GCD async()

Written by Paul Hudson    @twostraws

Swift offers you two ways to run code on the main thread: GCD and performSelector(onMainThread:). The first option looks like this:

DispatchQueue.main.async { [unowned self] in
    self.yourCodeHere()
}

The second option looks like this:

performSelector(onMainThread: #selector(yourCodeHere), with: nil, waitUntilDone: false)

The GCD option (the first one) has the advantage that you can write your code inline, whereas the second one requires a dedicated method you can call.

Available from iOS 4.0 – see Hacking with Swift tutorial 9

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