Dart Variables

Variables are fundamental building blocks in Dart programming. They serve as containers for storing and manipulating data within your code. Understanding how to declare, initialize, and use variables is crucial for effective Dart development.

Declaring Variables

In Dart, you can declare variables using various approaches. The most common method is to use the var keyword, which allows Dart to infer the variable's type:

var name = 'John Doe';
var age = 30;
var height = 1.75;

Alternatively, you can explicitly specify the variable type:

String country = 'Canada';
int population = 38000000;
double gdp = 1.643;

Variable Types

Dart supports several built-in data types, including:

• int: For whole numbers
• double: For floating-point numbers
• String: For text
• bool: For true/false values
• List: For ordered collections of objects
• Map: For key-value pairs

For more information on these types, refer to the Dart Data Types guide.

Variable Naming Conventions

When naming variables in Dart, follow these best practices:

• Use camelCase for variable names (e.g., firstName)
• Start with a lowercase letter
• Avoid using reserved keywords
• Choose descriptive names that reflect the variable's purpose

Variable Scope

Variables in Dart have different scopes depending on where they are declared. Local variables are confined to the block they're defined in, while top-level variables are accessible throughout the entire file.

void main() {
  var localVar = 'I am local';
  print(localVar); // Accessible
}

// Outside the main function
print(localVar); // Error: localVar is not defined in this scope

Null Safety

Dart 2.12 introduced null safety, a powerful feature that helps prevent null reference errors. With null safety, variables must be explicitly declared as nullable using the ? operator:

String? nullableString = null; // OK
String nonNullableString = 'Hello'; // OK
String nonNullableString = null; // Error

For more details on null safety, check out the Dart Null Safety guide.

Constants

Dart provides two ways to declare constants:

1. final: For runtime constants
2. const: For compile-time constants

final pi = 3.14159;
const gravity = 9.8;

Learn more about constants in the Dart Constants guide.

Late Variables

The late keyword allows you to declare non-nullable variables that are initialized after their declaration:

late String lateInitialized;
void someFunction() {
  lateInitialized = 'Now initialized';
  print(lateInitialized);
}

Conclusion

Understanding variables is crucial for mastering Dart programming. They form the foundation for data manipulation and storage in your applications. As you progress, explore more advanced concepts like Dart Operators and Dart Function Basics to enhance your Dart programming skills.