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

查看:25
本文介绍了将派生类传递给需要重写期望基类的方法的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

我有一个 A 类,有一个抽象方法 doAction(BaseClass obj) 需要一个 BaseClass 类型的参数

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,我有另一个类 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();
      }

 }

如果我需要将 DerivedClass 类型的参数传递给需要 BaseClass 的方法,我该如何处理?

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

你让基类泛型:

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

以及用派生类参数化的子类:

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 会违反 A 的合同:A 接受任何类型的 BaseClass,但您限制 B 只接受特定的子类.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.

这篇关于将派生类传递给需要重写期望基类的方法的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!

查看全文
登录 关闭
扫码关注1秒登录
发送“验证码”获取 | 15天全站免登陆