如何在dart中访问子类变量

class ParentClass {
  String parentVariable = "Parent Variable";
}

class ChildClass extends ParentClass {
  String childVariable = "Child Variable";
}

void main() {
  ChildClass child = ChildClass();
  print(child.childVariable); // 输出 "Child Variable"
}

class ParentClass {
  String parentVariable = "Parent Variable";

  void printVariable() {
    print(getVariable());
  }

  String getVariable() {
    return parentVariable;
  }
}

class ChildClass extends ParentClass {
  String childVariable = "Child Variable";

  @override
  String getVariable() {
    return childVariable;
  }
}

void main() {
  ChildClass child = ChildClass();
  child.printVariable(); // 输出 "Child Variable"
}