Swift make method parameter mutable?
As stated in other answers, as of Swift 3 placing var before a variable has been deprecated. Though not stated in other answers is the ability to declare an inout parameter. Think: passing in a pointer.
func reduceToZero(_ x: inout Int) { while (x != 0) { x = x-1 }}var a = 3reduceToZero(&a)print(a) // will print '0'This can be particularly useful in recursion.
Apple's inout declaration guidelines can be found here.
'var' parameters are deprecated and will be removed in Swift 3.So assigning to a new parameter seems like the best way now:
func reduceToZero(x:Int) -> Int { var x = x while (x != 0) { x = x-1 } return x}as mentioned here: 'var' parameters are deprecated and will be removed in Swift 3
For Swift 1 and 2 (for Swift 3 see answer by achi using an inout parameter): Argument of a function in Swift is let by default so change it to var if you need to alter the valuei.e,
func reduceToZero(var x:Int) -> Int { while (x != 0) { x = x-1 } return x}