Mixins

Mixins

About

• Mixins enable code reuse across hierarchies.
• Add capabilities without inheritance.
• Support multiple composition.
• Restricted using on clauses.

Main Topics

1. Basic Mixin

   • Definition: mixin keyword.
   • Example:

     mixin Logging {
       void log(String msg) => print(msg);
     }

2. Usage

   • **Definition: with` keyword.
   • Example:

     class Controller with Logging {...}

3. Restrictions

   • **Definition: on` keyword.
   • Example:

     mixin Auth on Controller {...}

4. Multiple Mixins

   • **Definition`: Linearization rules.
   • Example:

     class App with A, B, C {...}

How to Use

• Define: Create reusable behavior units
• Compose: Apply with with keyword
• Restrict: Use on for requirements
• **Order`: Last mixin takes precedence

How It Works

• Linearization: Depth-first order
• **No Instantiation`: Can’t be constructed
• **No Constructors`: Only methods/properties

Example Session:

void main() {
  var app = App();
  app.log('Message'); // From Logging mixin
}

Conclusion

Mixins provide flexible composition beyond inheritance, enabling orthogonal behavior reuse while maintaining clear ownership rules in Dart applications.