Assign Default Value for Parameter(s) in Function in Swift

Swift Function – Default Value for Parameter(s)

To assign default values for parameter(s) of a function in Swift, assign the parameter(s) with the required default value in the function definition.

The syntax to specify a default value for parameter of function is

func functionName(parameterName: Type = defaultValue) {
    //body
}

Example

In the following program, we will define a function add() with two parameters whose default value is 0.

main.swift

func add(a: Int = 0, b: Int = 0) {
    print(a+b)
}

add(a: 10, b: 20)
add(a: 5)
add(b: 4)

Output

For add(a: 10, b: 20) , we have passed values for both the parameters.

For add(a: 5) , we have passed value only for the parameter a. In this case, b would be considered 0 since the default value of b is 0.

Similarly, for add(b: 4) , we have passed value only for the parameter b. In this case, a would be considered 0 .

Now, let us define a function greet() that prints a greeting message to user. If accepts a String parameter. If no value is passed, it should consider the user name as just User. For this scenario, we will assign the default of name parameter to be User.

main.swift

func greet(name: String = "User") {
    print("Hello \(name)!")
}

greet()
greet(name: "Abc")

Output

Conclusion

In this Swift Tutorial, we learned how to assign a default value for parameter(s) in function definition.