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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.

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

Practice on your own: Online Dart compiler