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Type Inference with 'var'

Part of the Fundamentals section of Coddy's Dart journey — lesson 10 of 94.

In Dart, var enables type inference, where Dart automatically determines variable types from assigned values.

void main() {
  var name = 'Dart Programmer';
  print(name);
}

Dart infers name as String. It works with other types too:

void main() {
  var age = 25;              // Inferred as int
  var price = 19.99;         // Inferred as double
  var isAvailable = true;    // Inferred as bool
  
  print(age);          // Outputs: 25
  print(price);        // Outputs: 19.99
  print(isAvailable);  // Outputs: true
}

Challenge

Beginner

Create a Dart program that demonstrates type inference with the var keyword:

Declare a variable named name using var and assign it the string value "Dart"
Declare a variable named year using var and assign it the integer value 2011
Declare a variable named version using var and assign it the double value 2.19
Declare a variable named isStronglyTyped using var and assign it the boolean value true
Print each variable with a descriptive label in the following format:

Language: Dart
Created in: 2011
Current version: 2.19
Is strongly typed: true

Your output must match this exact format.

Cheat sheet

Use var for type inference - Dart automatically determines variable types from assigned values:

var name = 'Dart Programmer';  // Inferred as String
var age = 25;                   // Inferred as int
var price = 19.99;              // Inferred as double
var isAvailable = true;         // Inferred as bool

Try it yourself

void main() {
  // Declare your variables using var
  var name = ?;
  var year = ?;
  var version = ?;
  var isStronglyTyped = ?;
  
  // Print the variables with labels
  print("Language: " + name);
  print("Created in: " + year.toString());
  print("Current version: " + version.toString());
  print("Is strongly typed: " + isStronglyTyped.toString());
}

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 Parameters Functions Returning Values The '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