传递抽象参数到方法，为什么不？ [英] Pass abstract parameter to method, why not?

问题描述

我写了一个抽象类（使用 虚函数），我想有一个方法接受一个这样的类作为参数。鉴于类是抽象的，我理解我不能将一个抽象类传递给任何方法，但为什么不能将一个抽象类的子类传递给该方法？如何指定参数应该是指定基类的任何子类？

I've written an abstract class (with pure virtual functions), and I'd like to have a method accept one such class as a parameter. Given that the class is abstract, I understand that I couldn't pass an abstract class to any method, but why can't I pass a subclass of an abstract class to that method? How do I specify that a parameter should be any of the subclasses of a specified baseclass? This is all in C++.

推荐答案

您需要将参数指定为指针（或引用），例如。 Abstract * 而不是 Abstract 。如果 Derived 继承自 Abstract ，则可以传递 Derived * 当抽象* 是预期的，但是你不能通过传递类型 Derived code>需要抽象。

You need to specify the parameter as a pointer (or reference), e.g. Abstract * rather than Abstract. If Derived inherits from Abstract, you can pass a variable of type Derived * when Abstract * is expected, but you can't in general pass one of type Derived when Abstract is expected.

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