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iOS Functions in Swift Functions in Swift Functions in Code

Kanish Chhabra
Kanish Chhabra
2,151 Points
Posted by Kanish Chhabra
Kanish Chhabra
2,151 Points

Nil-Coalescing Operator

What is "Nil-Coalescing Operator"? I read this in the book published by apple on 'swift' but I wasn't able to understand it.

1 Answer

Michael Hulet
Michael Hulet
47,912 Points
Michael Hulet
Michael Hulet
47,912 Points

The nil coalescing operator (?? in code) returns the value on the value on the left if it's not nil, or the value on the right if it is nil, like this:

var first = "one"
let second = "two"

let test = first ?? second
// test is "one"

first = nil

let otherTest = first ?? second
// otherTest is "second"

This is especially useful for setting default values, like in functions where you otherwise can't or shouldn't, like this:

func someFunction(param: String?) -> Void{
    // arg is a non-optional String. It contains what was passed into param if it wasn't nil, or "Example" otherwise
    var arg = param ?? "Example"

    // The rest of the function's code goes here
}