Swift Introduction | Function Literals and Closures | Functions Are Values

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Swift

Swift functions have an important characteristic: they can be treated as values. A function groups together a process, but in Swift the function itself is also a value.

Run the following simple example.

func calc(num:Int)->Int {
    var res = 0
    for n in 0...num {
        res += n
    }
    return res
}
 
var f1 = calc
 
print(f1(10))

This example defines a function named calc. It assigns calc to the variable f1, then calls f1 with an argument.

The calc process runs correctly and returns a result. In other words, the calc function assigned to f1 works as expected.

Because functions are values, Swift can handle functions in a variety of ways. Remember this key point: a function is a value.