Interfaces trong Dart (implements)

class Printable {
  void print() {
    print('Printing...');
  }
}
 
class Document implements Printable {
  @override
  void print() {
    print('Printing document');
  }
}

class Printer {
  void print() {}
}
 
class Scanner {
  void scan() {}
}
 
class Copier {
  void copy() {}
}
 
class AllInOne implements Printer, Scanner, Copier {
  @override
  void print() => print('Printing');
  
  @override
  void scan() => print('Scanning');
  
  @override
  void copy() => print('Copying');
}

abstract class Drawable {
  void draw();
  void erase();
}
 
abstract class Movable {
  void move(int x, int y);
}
 
class Shape implements Drawable, Movable {
  @override
  void draw() => print('Drawing shape');
  
  @override
  void erase() => print('Erasing shape');
  
  @override
  void move(int x, int y) => print('Moving to ($x, $y)');
}

class Animal {
  String name;
  Animal(this.name);
  
  void eat() => print('$name is eating');
}
 
// extends: kế thừa implementation
class Dog extends Animal {
  Dog(String name) : super(name);
  // Kế thừa eat() từ Animal
}
 
// implements: phải implement lại tất cả
class Robot implements Animal {
  @override
  String name;
  
  Robot(this.name);
  
  @override
  void eat() => print('Robot cannot eat');
}

abstract class Animal {
  void breathe();
}
 
mixin Swimming {
  void swim() => print('Swimming');
}
 
class Fish extends Animal with Swimming implements Comparable<Fish> {
  int size;
  
  Fish(this.size);
  
  @override
  void breathe() => print('Breathing underwater');
  
  @override
  int compareTo(Fish other) => size.compareTo(other.size);
}

// Tách interface nhỏ
abstract class Readable {
  String read();
}
 
abstract class Writable {
  void write(String data);
}
 
abstract class Deletable {
  void delete();
}
 
class TextFile implements Readable, Writable, Deletable {
  String _content = '';
  
  @override
  String read() => _content;
  
  @override
  void write(String data) => _content = data;
  
  @override
  void delete() => _content = '';
}
 
class ReadOnlyFile implements Readable {
  final String _content;
  
  ReadOnlyFile(this._content);
  
  @override
  String read() => _content;
}

abstract class Repository<T> {
  T? findById(int id);
  List<T> findAll();
  void save(T item);
  void delete(int id);
}
 
class UserRepository implements Repository<User> {
  final List<User> _users = [];
  
  @override
  User? findById(int id) => 
      _users.firstWhere((u) => u.id == id);
  
  @override
  List<User> findAll() => List.from(_users);
  
  @override
  void save(User item) => _users.add(item);
  
  @override
  void delete(int id) => 
      _users.removeWhere((u) => u.id == id);
}