Parameters

Hello,

In this section, we will learn about the useful features of parameters in Swift language.

The first we will learn are variadic parameters.

A variadic parameter is a parameter that can take 0 or more values ​​of the same type. It can be used when we cannot predict exactly how many parameters it will take.

A function can have a maximum of one variadic parameter. 

Let's do an example.

func arithmeticMean(_ numbers: Double...) -> Double {
    var total: Double = 0
    for number in numbers {
        total += number
    }
    return total / Double(numbers.count)
}

var result = arithmeticMean(1, 2, 3, 4, 5)
print(result)
// returns 3.0, which is the arithmetic mean of these five numbers
result = arithmeticMean(3, 8.25, 18.75)
print(result)
// returns 10.0, which is the arithmetic mean of these three numbers

Variadic parameter actually creates a constant as a Constant array.

Function parameters are fixed by default.

Trying to change the parameter of a function inside the function body will result in a compile-time error.

If we want to write a function and want to change the value of the parameter of that function and we want this change to remain permanently even after the function is completed, we need to use an in-out parameter.

When calling the function, the argument is passed to the name of the variable with the & sign. This means that the variable can be changed by the function.

In-out parameters cannot have a default value. Variadic parameters cannot be marked as inout.

/* 
In the example below, the value of someInt 
is assigned to anotherInt and the value 
of anotherInt to someInt.
*/
// Note that these two types have variables.
func swapTwoInts(_ a: inout Int, _ b: inout Int) {
    let temporaryA = a
    a = b
    b = temporaryA
}

var someInt = 3
var anotherInt = 107

// Note that the corresponding arguments 
//are passed ampersant while calling the function.
swapTwoInts(&someInt, &anotherInt)


print("someInt is now \(someInt), and anotherInt is now \(anotherInt)")
// Prints "someInt is now 107, and anotherInt is now 3"

Congratulations 🎉

In this lesson, we have learned parameter features on Swift.

See you in the next lesson.