如何检查对象的类型是否是 C++ 中的特定子类?

2021-12-09 00:00:00 class subclass identification c++

我正在考虑使用 typeid() 但我不知道如何询问该类型是否是另一个类的子类(顺便说一下，它是抽象的)

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.如果您的程序需要知道一个对象是什么类，这通常表明存在设计缺陷.看看你是否可以使用虚函数获得你想要的行为.此外，有关您正在尝试执行的操作的更多信息会有所帮助.

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，那么尝试做这样的事情:

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();
}

由于关于这个答案的争论在这么多年后仍在继续，我想我应该提供一些参考资料.如果您有一个指向基类的指针或引用，并且您的代码需要知道对象的派生类，那么它违反了 Liskov 替换原则.鲍勃叔叔 称之为对面向对象设计的诅咒".

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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