Swift Introduction | Functions | Variadic Parameters

Use a variadic parameter when you do not know how many values will be passed to a function.

(argumentName:Type...)

Callers can provide multiple comma-separated values for this parameter. The function receives those values as an array. You can think of a variadic parameter as an array parameter.

func calc(nums:Int...) -> Int {
    var total:Int = 0
    for num in nums {
        total += num
    }
    return total
}
calc(1,2,3,4,5)

The declaration is:

calc(nums:Int...) 

The call is:

calc(1,2,3,4,5) 

Multiple values are passed through nums. Inside the function, iterate over them with for.

for num in nums {...

The number of elements in a variadic parameter is not fixed. Processing it with a for statement is the usual approach.