Implicit Interfaces

Implicit Interfaces

About

• Every class implicitly defines an interface.
• No separate interface definition needed.
• Enables duck typing.
• Supports multiple interface implementation.

Main Topics

1. Basic Implementation

   • Definition: implements keyword.
   • Example:

     class MockList implements List {...}

2. Multiple Interfaces

   • Definition: Composing behaviors.
   • Example:

     class Employee implements Person, Identifiable {...}

3. Partial Implementation

   • Definition: Must implement all members.
   • Example:

     class MockButton implements Button {
       @override void onPress() {...}
       // Must implement all Button members
     }

4. Testing Advantages

   • Definition: Easy mock creation.
   • Example:

     class MockAuth implements AuthService {...}

How to Use

• Implement: Any class as interface
• Compose: Multiple class interfaces
• Mock: Create test doubles easily
• Document: Interface expectations

How It Works

• Contracts: All public members become interface
• Verification: Compiler enforces completeness
• Flexibility: No formal interface definition needed

Example Session:

void main() {
  var mock = MockList(); // Implements List interface
  print(mock.length);
}

Conclusion

Dart’s implicit interfaces provide flexible contract implementation without ceremony, particularly valuable for testing and adapting existing classes to new interfaces.