Static function variables in Swift

Solution 1:

I don't think Swift supports static variable without having it attached to a class/struct. Try declaring a private struct with static variable.

func foo() -> Int {
    struct Holder {
        static var timesCalled = 0
    }
    Holder.timesCalled += 1
    return Holder.timesCalled
}

  7> foo()
$R0: Int = 1
  8> foo()
$R1: Int = 2
  9> foo()
$R2: Int = 3

Solution 2:

Another solution

func makeIncrementerClosure() -> () -> Int {
    var timesCalled = 0
    func incrementer() -> Int {
        timesCalled += 1
        return timesCalled
    }
    return incrementer
}

let foo = makeIncrementerClosure()
foo()  // returns 1
foo()  // returns 2

Solution 3:

Swift 1.2 with Xcode 6.3 now supports static as expected. From the Xcode 6.3 beta release notes:

“static” methods and properties are now allowed in classes (as an alias for “class final”). You are now allowed to declare static stored properties in classes, which have global storage and are lazily initialized on first access (like global variables). Protocols now declare type requirements as “static” requirements instead of declaring them as “class” requirements. (17198298)

It appears that functions cannot contain static declarations (as asked in question). Instead, the declaration must be done at the class level.

Simple example showing a static property incremented inside a class (aka static) function, although a class function is not required:

class StaticThing
{
    static var timesCalled = 0

    class func doSomething()
    {
        timesCalled++

        println(timesCalled)
    }
}

StaticThing.doSomething()
StaticThing.doSomething()
StaticThing.doSomething()

Output: