如何检查对象的类型是否是C ++中的特定子类？ [英] How do I check if an object's type is a particular subclass in C++?

问题描述

我一直在使用typeid（），但我不知道如何问，如果该类型是另一个类的子类（顺便说一下，是抽象的）

I was thinking along the lines of using typeid() but I don't know how to ask if that type is a subclass of another class (which, by the way, is abstract)

推荐答案

你真的不应该。如果你的程序需要知道一个对象是什么类，这通常表示设计缺陷。看看你是否可以使用虚拟函数获得所需的行为。

You really shouldn't. If your program needs to know what class an object is, that usually indicates a design flaw. See if you can get the behavior you want using virtual functions. Also, more information about what you are trying to do would help.

我假设你有这样的情况：

I am assuming you have a situation like this:

class Base;
class A : public Base {...};
class B : public Base {...};

void foo(Base *p)
{
  if(/* p is A */) /* do X */
  else /* do Y */
}

如果这是你所拥有的，那么尝试这样做：

If this is what you have, then try to do something like this:

class Base
{
  virtual void bar() = 0;
};

class A : public Base
{
  void bar() {/* do X */}
};

class B : public Base
{
  void bar() {/* do Y */}
};

void foo(Base *p)
{
  p->bar();
}

修改继续这么多年，我以为我应该引用一些参考。如果你有一个指针或对一个基类的引用，你的代码需要知道对象的派生类，那么它违反 Liskov替代原则。 叔叔叔叔将此称为 anathema to Object Oriented Design 。

Since the debate about this answer still goes on after so many years, I thought I should throw in some references. If you have a pointer or reference to a base class, and your code needs to know the derived class of the object, then it violates Liskov substitution principle. Uncle Bob calls this an "anathema to Object Oriented Design".

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