What is abstraction in programming?

Abstraction is a mechanism that allows hiding implementation details and showing only the necessary information. In the context of OOP, abstraction is achieved through abstract classes and interfaces. They define a contract (a set of methods) that concrete classes must implement without revealing how these methods work.

Advantages of abstraction:

• Simplification of complex systems.
• Increased flexibility and extensibility.
• Reduced dependency between modules.
• Improved maintainability of code.

Example of an abstract class in Flutter:

// Defines the basic behavior of a data repository
abstract class DataRepository {
  // Abstract method for fetching data, without implementation details
  Future<List<String>> fetchData();

  // Can contain an implemented method if it is common for all subclasses
  void dispose() {
    // Resource release logic if needed
  }
}

// Concrete implementation of a repository from an external source
class RemoteDataRepository implements DataRepository {
  @override
  Future<List<String>> fetchData() async {
    // Details of fetching data over the network
    await Future.delayed(Duration(seconds: 2)); // Simulating delay
    return ['Data from network 1', 'Data from network 2'];
  }
}

// Concrete implementation of a repository from cache
class CacheDataRepository implements DataRepository {
  @override
  Future<List<String>> fetchData() async {
    // Details of fetching data from local cache
    return ['Data from cache 1', 'Data from cache 2'];
  }
}

Here, DataRepository abstracts the process of data fetching, allowing work with different data sources (remote or cache) through a unified interface. Client code interacts only with DataRepository, without knowing the specific implementation.