class01 extends

class01extends.dart

void main(){
  
  Parent p1 = Parent();
  Child c1 = Child();
  Parent pc1 = Child();
  
  p1.a;
  // p1.b; // err -> only child
  p1.func();
  p1.func3();
  // p1.func2(); // err -> only child
  p1.func4();
  
  c1.a;
  c1.b;
  c1.func();
  c1.func2();
  c1.func3();
  print( c1.func4() );
  
  // ------------------------------------------------------
  
  final p2 = Parent2(a:1);
  final c2 = Child2(a: 2);
}


class Parent{
  int a = 11;
  
  void func() => print(this.a);
  void func3() => print(this.a);
  int func4() => this.a*2;
}

class Child extends Parent{
  
  int b = 22;
  
  void func2() => print(this.a+this.b);
  @override
  void func3() => print(this.a * this.b);
  @override
  int func4() => super.func4() * 2;
}


class Parent2{
  final int a;
  Parent2({required this.a});
}
class Child2 extends Parent2{
  // (1)
  Child2({required super.a});
  // (2)
  // Child2({required int b}) : super(a: b);
}