Default parameter values in Swift

Introduction

Default parameter values let you give a starting value to a function's input. This way, if you don't provide that input, the function still works smoothly.

When you want a function to work even if some inputs are missing.

When you want to avoid writing many versions of the same function.

When you want to provide common or typical values automatically.

When you want to make your code easier to use and read.

Syntax

Swift

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

You write the default value after an equals sign = in the parameter list.

If you call the function without that parameter, the default value is used.

Examples

This function says hello. If you don't give a name, it uses "Friend".

Swift

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

This function multiplies a number by a multiplier. If you don't give the multiplier, it doubles the number.

Swift

func multiply(number: Int, by multiplier: Int = 2) -> Int {
    return number * multiplier
}

Sample Program

This program shows how the greet function works with and without giving a name.

Swift

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

greet()
greet(name: "Alice")

Important Notes

Default parameters must come after parameters without defaults.

You can mix parameters with and without default values in the same function.

Summary

Default parameter values make functions easier to call by providing fallback inputs.

They help avoid writing many similar functions.

Use them to make your code cleaner and friendlier.