将派生类传递给需要覆盖期望基类的方法 [英] Passing Derived Class to a method which needs to override expecting a base class

问题描述

我有一个类A，抽象方法doAction（BaseClass obj）期望一个类型为BaseClass的参数

I have a class A, with an abstract method doAction(BaseClass obj) expecting a param of type BaseClass

public class A {
    //....
    abstract void doAction(BaseClass obj);
    //....
}

现在，我有另一个班级B需要扩展A.但是，B的doAction方法需要使用扩展BaseClass的对象DerivedClass。

Now, I have another class B which needs to extend A. However, B's doAction method needs to use an object DerivedClass which extends BaseClass.

public class B extends class A {
     //..
     void doAction(DerivedClass obj) {
          obj.callMethodAvailableOnlyInDerivedClass();
      }

 }

我如何处理这种情况我需要将类型为DerivedClass的param传递给要覆盖的方法，同时期望一个BaseClass？

How do I handle this situation where I need to pass param of type DerivedClass to the method to be overridden while it is expecting a BaseClass ?

谢谢！

推荐答案

您使基类具有通用性：

public class A<T extends BaseClass> {
    //....
    abstract void doAction(T obj);
    //....
}

以及参数化的子类派生类：

and the subclass parameterized with the derived class:

public class B extends A<DerivedClass> {
     //..
     void doAction(DerivedClass obj) {
         obj.callMethodAvailableOnlyInDerivedClass();
     }
}

没有泛型，这是不可能的，因为B会打破A：A的契约接受任何类型的BaseClass，但是您将B限制为仅接受特定的子类。这不尊重 Liskov原则。

Without generics, it's not possible because B would break the contract of A: A accepts any kind of BaseClass, but you retrict B to only accept a specific subclass. This does not respect the Liskov principle.

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