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Functions Returning Values

Part of the Fundamentals section of Coddy's Dart journey — lesson 68 of 94.

Functions returning values allow your code to calculate a result and send it back to where the function was called. Unlike void functions, these functions specify a return type.

Create a function that returns an integer:

int add(int a, int b) {
  return a + b;
}

void main() {
  int sum = add(5, 3);
  print('Sum: $sum');
}

After executing the above code, the output will be:

Sum: 8

The function calculates the sum and returns it with the return keyword. The returned value is stored in the sum variable.

Challenge

Beginner

In this challenge, you'll practice creating a function that returns a value. Functions can calculate a result and return it to be used elsewhere in your code.

Complete the calculateSquare function below. It should:

Take an integer parameter number
Calculate the square of that number (multiply it by itself)
Return the result

The expected output is:

The square of 5 is: 25

Cheat sheet

Functions can return values by specifying a return type and using the return keyword:

int add(int a, int b) {
  return a + b;
}

void main() {
  int sum = add(5, 3);
  print('Sum: $sum'); // Output: Sum: 8
}

The returned value can be stored in a variable and used elsewhere in your code.

Try it yourself

void main() {
  // This number is already defined for you
  int number = 5;
  
  // Call the calculateSquare function and store the result
  int result = calculateSquare(number);
  
  // This will display the result
  print('The square of $number is: $result');
}

// TODO: Complete this function to return the square of the number
int calculateSquare(int number) {
  // Your code here - calculate the square and return it
  
}

Test yourself

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

All lessons in Fundamentals

1Introduction to Dart

What is Dart?The main Function Printing Output Code Comments

4Operators Part 2

Comparison Operators Logical AND Logical OR Logical NOT Type Test Operators Recap - Making Comparisons

7Working with Strings

String Concatenation String Interpolation Multi-line Strings String Properties Basic String Methods

10Collections - Maps Basics

What are Maps?Creating a Map Accessing Values by Key Key-Value Pairs Getting Map Size Getting Keys Getting Values Checking if a Key Exists

13Null Safety In Depth

Understanding Null Nullable Types Non-Nullable Types Null Assertion Operator Late Initialization Recap - Handling Null Safely

16Fundamentals Challenges

Challenge: List of calculation Challenge: Sum of numbers Challenge: Find product

2Variables and Basic Data Types

What are Variables?Strings Integers (int)Doubles (double)Booleans (bool)Type Inference with 'var'Final Variables Constant Variables Naming Conventions Basic Null Safety Recap - Declaring Variables

5Operators Part 3

Null-aware Operator Null-aware Access Conditional Operator

8Control Flow - Loops

The 'for' Loop The 'while' Loop The 'do-while' Loop Using 'break' in Loops Using 'continue' in Loops Recap - Repeating Code

11Functions Basics

What are Functions?Defining a Basic Function Calling a Function Functions with ParametersFunctions Returning ValuesThe 'void' Keyword Arrow Syntax Recap - Simple Functions

14Type Conversion

Converting String to int Converting String to double Converting Numbers to String Handling Conversion Errors

3Operators Part 1

Arithmetic Operators Integer Division Modulo Operator Increment and Decrement Assignment Shortcuts Recap - Simple Calculations

6Control Flow - Decision Making

The 'if' Statement The 'else' Statement The 'else if' Statement Recap - Simple Decisions Nested 'if' Statements The 'switch' Statement

9Collections - Lists Basics

What are Lists?Creating a List Accessing by Index Getting List Length Adding Elements Removing Elements Checking if a List is Empty Iterating Over a List

12Functions Advanced

Optional Positional Parameters Named Parameters Required Named Parameters Default Parameter Values Recap - Function Parameters

15Project: Simple Calculator

Setting Up Declaring Number

Project lesson

Creating an Operation

Project lesson

Performing Calculation

Project lesson

Displaying Result

Project lesson