Functions in Dart

Definition

A function is a reusable block of code that performs a specific task. Functions help you organize code, reduce duplication, and make programs easier to understand and maintain.

Function Syntax

returnType functionName(parameterType parameterName) {

// Function body

return value;

}

Key Components

Return Type

Specifies what type of value the function returns

Use `void` if the function returns nothing

Examples: `int`, `String`, `double`, `bool`

Parameters

Input values passed to a function

Each parameter has a type and name

A function can have zero or multiple parameters

Function Call

When you use a function, you "call" it

Pass arguments (actual values) that match the parameters

The function executes and returns a result

Cell2Dart

// Simple function with parameters and return value int add(int a, int b) { return a + b; } // Call the function int result = add(5, 3); print('5 + 3 = $result'); // Another example String greet(String name) { return 'Hello, $name!'; } String message = greet('Dart'); print(message);

Understanding the Call Stack

When a function is called:

1. **Push**: The function is added to the call stack

2. **Execute**: The function body runs

3. **Return**: The function returns a value

4. **Pop**: The function is removed from the stack

The **call stack** (shown on the right) shows which functions are currently running. When main() calls add(), add() appears on top of the stack. When add() finishes, it's removed.

Cell4Dart

// Function calling another function int multiply(int a, int b) { return a * b; } int calculate(int x, int y) { int product = multiply(x, y); return product + 10; } int result = calculate(3, 4); print('Result: $result');

Void Functions

Functions that don't return a value use the `void` return type. They perform an action but don't send data back.

Function Benefits

**Reusability**: Write once, use many times

**Readability**: Code is organized and easier to understand

**Maintainability**: Changes in one place affect all uses

**Testing**: Individual functions can be tested separately

Cell6Dart

// Function with no return value (void) void printMultipleTimes(String message, int times) { for (int i = 0; i < times; i++) { print(message); } } printMultipleTimes('Dart', 3);

Practice

CellcustomDart

void greet(String name) { print('Hello, $name!'); } greet('Dart');