Swift: function with default parameter before non-default parameter

Question

say I have a function that has non-default parameter after default parameter like this:

func f(first:Int = 100, second:Int){}

how can I call it

Answer 1

On Swift 3:

func defaultParameterBefore(_ x: Int = 1, y: Int ) {}

Calling

defaultParameterBefore(2)

will raise this error

error: missing argument for parameter 'y' in call

The only exception is:

• There is a parameter before the default parameter;
• and the parameter after the default parameter is a closure;
• and the closure parameter is the last parametr;
• and calling via trailing closure

For example:

func defaultParameterBetween(_ x: Int, _ y: Bool = true, _ z: String) {
    if y {
       print(x)
    } else
       z()
    }
}

// error: missing argument for parameter #3 in call
// defaultParameterWithTrailingClosure(1, { print(0) }

// Trailing closure does work, though.
func defaultParameterWithTrailingClosure(_ x: Int, y: Bool = true,
                                     _ z: () -> Void) {
    if y {
        print(x)
    } else {
        z()
    }
}

defaultParameterWithTrailingClosure(1) { print(0) }

swift version: DEVELOPMENT-SNAPSHOT-2016-04-12