Understanding Swift 2.2 Selector Syntax - #selector()

Question

I am switching over the syntax of my project toward Swift 2.2 (which xCode helps me do automatically); however, I do not understand the new #selector() syntax.<

Answer 1

This is the way Swift method signatures are represented in documentation, and it is now beginning to be used in new language features such as the #selector() syntax to express methods by their argument lists.

The each colon (:) represents a method parameter. For named parameters, the colon is preceded by the external parameter name; for unnamed parameters, an underscore (_) is used.

So for example, MyVC.timerCalled(_:)) indicates a method on the MyVC type with one unnamed parameter, which might be declared like this:

func timerCalled(timer: NSTimer) { ... }

(Note that timer is the internal parameter name, since by default the first parameter of a method is unnamed)

The type (MyVC in your example) can also be omitted if it is within the same scope of the #selector() declaration.

A more complex example might look like this:

let sel = #selector(aMethodWithSeveralParameters(_:secondParam:thirdParam:))

...

func aMethodWithSeveralParameters(firstParam: Int, secondParam: Int, thirdParam: Int) { ... }