Swift version: 5.0
You can use
perform(_:with:afterDelay:) to run a method after a certain number of seconds have passed, but if you want to run code at a specific time – say at exactly 4pm – then you should use
Timer instead. This class is great for executing code repeatedly at a specific time interval, but it's also great for running code at an exact time that you specify.
This is accomplished using a
Timer constructor that accepts an
Date for when the timer should fire. You can make this date however you want, which is what makes this approach so flexible.
As a simple example, this will create a timer that calls a
runCode() method in five seconds:
let date = Date().addingTimeInterval(5) let timer = Timer(fireAt: date, interval: 0, target: self, selector: #selector(runCode), userInfo: nil, repeats: false) RunLoop.main.add(timer, forMode: .common)
Notice how you can specify a
interval parameter? That's for when you set
repeats to be
true. If you have a
Date 5 seconds from now and an
interval of 1 (after setting
repeat to be true!), it means "call
runCode() after five seconds, then every one second after that."
Available from iOS 2.0
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.