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How to convert a String to an Int

Swift version: 5.6

Paul Hudson    @twostraws   

If you have an integer hiding inside a string, you can convert between the two just by using the integer's initializer, like this:

let myString1 = "556"
let myInt1 = Int(myString1)

Because strings might contain something that isn’t a number – e.g. “Fish” rather than “556” – the Int initializer will return an optional integer, so if you want to force a value you should use nil coalescing like this:

let myInt2 = Int(myString) ?? 0

That means “attempt to convert myString to an integer, but if the conversion failed because it contained something invalid then use 0 instead.”

As with other data types (Float and Double) it’s also possible to convert by using NSString if you’re desperate:

let myInt3 = (myString1 as NSString).integerValue

Ideally, though, that shouldn’t needed.

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