如何检查模板参数的类型？ [英] How to check for the type of a template parameter?

问题描述

假设我有一个模板函数和两个类

Suppose I have a template function and two classes

class animal {
}
class person {
}

template<class T>
void foo() {
  if (T is animal) {
    kill();
  }
}

如何检查T是动物？我不想有
在运行时检查的东西。感谢

How do I do the check for T is animal? I don't want to have something that checks during the run time. Thanks

推荐答案

使用 is_same ：

#include <type_traits>

template <typename T>
void foo()
{
    if (std::is_same<T, animal>::value) { /* ... */ }  // optimizable...
}

通常，这是一个完全不可行的设计， ：

Usually, that's a totally unworkable design, though, and you really want to specialize:

template <typename T> void foo() { /* generic implementation  */ }

template <> void foo<animal>()   { /* specific for T = animal */ }

使用显式（非推导）参数的函数模板是不寻常的。这是不是没有闻到，但通常有更好的方法。

Note also that it's unusual to have function templates with explicit (non-deduced) arguments. It's not unheard of, but often there are better approaches.

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