Dart Flutter 导入和扩展的区别是什么？

Question

I still do not understand the difference between importing a class and extending a class. I mean if I just import the class I can still use its constructor and methods, so what is the advantage of using extends ?

Feel free to use the two classes I provided or change them to your convenience.

Class A {
  final String a;
  A({this.a});
  void printA(){
    print(this.a);
  }
}

Class B {
  final String b;
  B({this.b});
  void printB(){
    print(this.b);
  }
}

Answer 1

An import statement makes another class visible in that file.

The extends keyword makes a class inherit from another class.

When you say class B extends A , B has inherited all the properties and methods of A.

As a reference: https://medium.com/run-dart/dart-dartlang-introduction-object-oriented-programming-c3d79d94d303