Calling a Method After Delay

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When prototyping or orchestrating animations, it is sometimes useful to run a method after some delay.

Step 1: Add the delay method

Because the mechanism for using Grand Central Dispatch is a bit ugly, it's useful to wrap it up into a convenient function. Put the function below into each view controller that you want to use it.

func run(after wait: TimeInterval, closure: @escaping () -> Void) {
    let queue = DispatchQueue.main
    queue.asyncAfter(deadline: DispatchTime.now() + wait, execute: closure)
}

Step 2: Use the delay method

To run code after a delay, simply call the method, as below. Since the code in the braces is a closure, you have to use self to refer to your class methods and variables.

// Delay for 2 seconds, then run the code between the braces.
let secondsToDelay = 2.0
run(after: secondsToDelay) {
   // This code will run after the delay
}