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iOS Swift Closures Closures and Closure Expressions Closure Expression Syntax

Posted by Roland Shen
Roland Shen
7,628 Points

Why assign a function to a variable?

What is the point of assigning a function to a variable when you can just call the function in another set of parameters? For example: 

func doubler(i: Int) -> Int {
    return i * 2
}

let doubled = doubler

var numbers: [Int] = [1,2,3,4,5]

var doubledNumbers = numbers.map(doubled)

Why cant you just write out numbers.map(doubler())? Also, how come no parameters are needed when calling the function?

1 Answer

Gene Osborne
Gene Osborne
8,630 Points

You can do exactly that.

Some people like to include extra steps such as this one, so that the code is a little easier to read (a matter of opinion).

You are correct, though, that it is not necessary.

In addition, I feel it is worth mentioning that if you assign the function to a variable, you can use that variable multiple times without calling the method multiple times. This matters for methods that may take a lot of time and/or space to execute. For such methods, minimizing the number of calls to the method may be essential to the program running smoothly.