Differences Between Dart 2.x and Earlier Versions

Dart 2.x introduced several significant changes and improvements over its earlier versions, focusing on enhancing performance, type safety, and developer experience. This document outlines the key differences, along with sample code to illustrate these changes.

1. Sound Null Safety

One of the most notable features introduced in Dart 2.x is sound null safety. This feature ensures that variables cannot be null unless explicitly declared as nullable, helping to prevent null reference errors.

Example of Sound Null Safety

void main() {
    String name = 'Alice'; // Non-nullable
    // name = null; // This will cause a compile-time error

    String? nullableName; // Nullable type
    nullableName = null; // This is allowed
    print(nullableName); // Output: null
}

2. Type Inference and Type Annotations

Dart 2.x improved type inference, allowing the compiler to infer types more effectively, reducing the need for explicit type annotations. This makes the code cleaner and easier to read.

Example of Type Inference

void main() {
    var name = 'Alice'; // Type inferred as String
    var age = 30; // Type inferred as int
    print('$name is $age years old.');
}

3. Enhanced Collections

Dart 2.x introduced new collection types and improved existing ones, making it easier to work with lists, sets, and maps.

Example of Enhanced Collections

void main() {
    var numbers = <int>[1, 2, 3]; // List of integers
    var names = <string>{'Alice', 'Bob'}; // Set of strings
    var ages = <string, int>{'Alice': 30, 'Bob': 25}; // Map of string to int

    print(numbers);
    print(names);
    print(ages);
}
</string,></string></int>

4. Improved Asynchronous Programming

Dart 2.x enhanced support for asynchronous programming with better handling of Future and Stream types, making it easier to write non-blocking code.

Example of Asynchronous Programming

import 'dart:async';

Future<void> fetchData() async {
    await Future.delayed(Duration(seconds: 2));
    print('Data fetched!');
}

void main() {
    print('Fetching data...');
    fetchData();
    print('Waiting for data...');
}
</void>

5. Improved Tooling and Libraries

Dart 2.x came with improved tooling, including better support for IDEs and enhanced libraries for common tasks, making development more efficient.

Example of Using Libraries

import 'dart:math';

void main() {
    var random = Random();
    print('Random number: ${random.nextInt(100)}');
}

6. Removal of Deprecated Features

With Dart 2.x, several deprecated features were removed to streamline the language and improve performance. This includes the removal of the var keyword for function parameters and the dynamic type in certain contexts.

Example of Removed Features

void main() {
    // The following would cause an error in Dart 2.x
    // dynamic name = 'Alice'; // Avoid using dynamic unless necessary
}

7. Conclusion

Dart 2.x introduced significant improvements over earlier versions, focusing on sound null safety, enhanced type inference, improved collections, better asynchronous programming support, and streamlined tooling. These changes make Dart a more robust and developer-friendly language for building applications across various platforms.