你如何创建一个可选变量，在 Swift 中分配一个函数

Question

I would like to create an optional variable that can be assigned a function ( or can be nil). I'm guessing it would look something like this but the following code does not compile.

var variableThatWillBeAssignedAFunction: {(Int) -> Int}?

Thanks for your help

Answer 1

var variableThatWillBeAssignedAFunction: ((Int) -> Int)?

To make it more readable, you can also use a typealias:

typealias IntegerTransform = (Int) -> Int
var variableThatWillBeAssignedAFunction: IntegerTransform?