In Dart, every class implicitly defines an interface, which means the public members of a class can be implemented by other classes. Unlike some languages, Dart does not have a separate interface keyword. Instead, you use the implements keyword to create a class that agrees to provide concrete implementations for all the methods and properties of the interface.
For example:
class Vehicle {
void start() {}
void stop() {}
}
// Implementing Vehicle as an interface
class Car implements Vehicle {
@override
void start() {
print('Car started');
}
@override
void stop() {
print('Car stopped');
}
}
Here, Car implements the Vehicle interface and provides concrete implementations for start() and stop(). Unlike extending a class, implementing an interface does not inherit the implementation, it only enforces the contract.
I’ve applied interfaces in Flutter projects when creating service layers. For example, I defined an interface ApiService with methods like fetchData() and postData(). Then, multiple classes implemented this interface for different APIs, which ensured that all API services adhered to the same method structure, making the code modular and testable.
A challenge I faced was that implementing an interface requires providing all methods explicitly, even if some methods were already implemented in another class. A limitation is that this can lead to boilerplate code if many methods exist. An alternative for sharing some common behavior while enforcing a contract is to use abstract classes or combine abstract classes with mixins.