Swift version: 5.4
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."
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Available from iOS 2.0
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
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