- Abstract Classes:
- Abstract classes cannot be instantiated and can only be inherited by other classes.
- Abstract classes allow you to define constructors, which can be reused in subclasses.
- Abstract classes can contain methods with concrete implementations, enabling you to provide default behavior for subclasses.
- Abstract classes are typically used to define a common base framework, allowing subclasses to inherit and implement or override specific functionalities.
- Interfaces:
- Dart does not have a dedicated 'interface' keyword; any class can serve as an interface.
- When a class is used as an interface, classes implementing it must override all methods unless these methods have already been implemented elsewhere.
- Interfaces are primarily used to define a set of APIs that can be implemented by multiple unrelated classes, which may originate from different class hierarchies.
- Interfaces emphasize the behavior pattern for achieving multiple inheritance, meaning a class can implement multiple interfaces to combine various behaviors.
In summary, abstract classes are more commonly used as a base template for inheritance, providing common functionality, whereas interfaces define a set of behaviors that must be concretely implemented by the implementing classes. In practice, choosing between abstract classes and interfaces depends on your specific requirements: whether you need to inherit some implementations from a base class or require multiple classes to adhere to a clear contract.