My Question is the below example in function and closure why we need to use this line
func sumOf(numbers: Int...)
with three dots (...) ?
func sumOf(numbers: Int...) -> Int {
var sum = 0
for number in numbers {
sum += number
}
return sum
}
sumOf()
sumOf(42, 597, 12)
what is meaning for these dots ??
Those ... mean that the function can take a variable number of arguments
From the The Swift Programming Language book:
Variadic Parameters
A variadic parameter accepts zero or more values of a specified type. You use a variadic parameter to specify that the parameter can be passed a varying number of input values when the function is called. Write variadic parameters by inserting three period characters (...) after the parameter’s type name.
The values passed to a variadic parameter are made available within the function’s body as an array of the appropriate type. For example, a variadic parameter with a name of numbers and a type of Double... is made available within the function’s body as a constant array called numbers of type [Double].
I do not know about Swift, but in other languages such as ActionScript, the dots means you can pass more than one argument to the method and they will be interpreted as an array.
For example:
sumOf(1, 3, 6);
This is known as a variadic parameter and accepts zero or more Int values. For more information see https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Functions.html
It means you can pass in any number of ints rather than an explicitly specified number
if you said
func sumOf(num1: Int, num2: Int) -> Int
you could only sum 2 Ints and you would need to write a new function for 3 and 4 etc.
In essence it is a shorthand for writing
func sumOf(numbers :[Int]) -> Int
which does not require the caller to wrap the numbers in an array.
The ... here represent that the function can take as many number of arguments of type Int.
You can consider this as you're passing an array as a parameter except that you are not gonna use the Square Notation([]).
This means that the function can take variable number of arguments, collecting them into an array.
and that parameter, in your case numbers is called variadic parameter.
Note, in swift 2, a function can have maximum one variadic parameter
