Default Values

Part of the Fundamentals section of Coddy's Swift journey — lesson 57 of 86.

Sometimes a parameter has a value that's used most of the time. Instead of requiring the caller to provide it every time, you can assign a default value to that parameter.

To set a default value, use the assignment operator (=) after the parameter's type:

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

greet(name: "Alice")                    // Output: Hello, Alice!
greet(name: "Bob", greeting: "Hi")      // Output: Hi, Bob!

When calling the function, you can omit parameters that have default values. Swift will use the default automatically. But if you need a different value, you can still provide one explicitly.

Parameters with default values should be placed at the end of the parameter list. This keeps function calls clean and readable:

func calculatePrice(base: Double, taxRate: Double = 0.1) -> Double {
    return base + (base * taxRate)
}

print(calculatePrice(base: 100))              // Output: 110.0
print(calculatePrice(base: 100, taxRate: 0.2)) // Output: 120.0

Default values make your functions more flexible—they work simply for common cases while still allowing customization when needed.

Challenge

Easy

Write a function formatGreeting that takes name, greeting, and repeatCount and returns a formatted greeting message.

The function should use default values for the optional parameters:

greeting should default to "Hello"
repeatCount should default to 1

Build a string that repeats the greeting pattern the specified number of times, separated by spaces.

Parameters:

name (String): The person's name (required)
greeting (String): The greeting word (default: "Hello")
repeatCount (Int): How many times to repeat the greeting (default: 1)

Returns: A string with the greeting pattern repeated. Format: "[greeting], [name]!" repeated repeatCount times, separated by a single space (String)

For example, if name is "Alice", greeting is "Hi", and repeatCount is 2, the function returns "Hi, Alice! Hi, Alice!".

If called with just name as "Bob" (using defaults), it returns "Hello, Bob!".

Cheat sheet

To set a default value for a parameter, use the assignment operator (=) after the parameter's type:

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

greet(name: "Alice")                    // Output: Hello, Alice!
greet(name: "Bob", greeting: "Hi")      // Output: Hi, Bob!

When calling a function, you can omit parameters that have default values. Swift will use the default automatically, but you can still provide a different value explicitly if needed.

Parameters with default values should be placed at the end of the parameter list:

func calculatePrice(base: Double, taxRate: Double = 0.1) -> Double {
    return base + (base * taxRate)
}

print(calculatePrice(base: 100))              // Output: 110.0
print(calculatePrice(base: 100, taxRate: 0.2)) // Output: 120.0

Try it yourself

func formatGreeting(name: String, greeting: String, repeatCount: Int) -> String {
    // Write code here
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Fundamentals

1Introduction

The Language Hello World!Comments

4Operators Part 1

Arithmetic Operators Modulo Operator Compound Assignment Recap - Simple Math Comparison Operators

7Basic IO

Print Function String Interpolation ReadLine Input Type Conversion Recap - Till 120 Recap - True or False

10Functions

Declare A Function Parameters And Arguments Return Values Argument Labels Recap - Sigma Function Recap - Validation FunctionDefault Values

13Iterating Over Sequences

Iterating Over Elements The Enumerated Method Iterating Over Strings P1 Iterating Over Strings P2

16Final Challenges

Flat Asterisk Pyramid Pattern Finder What To Buy

2Variables

Let vs Var Type Annotations Numbers String Boolean Naming Conventions Recap - Initialize Variables

5Operators Part 2

Logical Operators Part 1 Logical Operators Part 2 Recap - Simple Logic Logical Operators Part 3 Ternary Operator

8Bill Split Calculator

Welcome Message Getting Input

Calculating Tip And Total

Splitting The Bill

Formatted Output

11FizzBuzz with a Twist

Game Overview The FizzBuzz Function

Looping The Numbers

Adding The Twist

14Arrays Advanced

Array Slicing Part 1 Array Slicing Part 2 Sequence Operators The Contains Method