是否可以从（Functor成员的）函数签名中检索参数类型以在模板中使用？ [英] Is it possible to retrieve the argument types from a (Functor member's) function signature for use in a template?

问题描述

假设你有一个函子：

struct MyFunctor
{
    bool operator ()( int value )
    {
        return true;
    }
};

是否可以检索函子的成员参数类型以在模板中使用？下面是这个神话功能的用途：

Is it possible to retrieve a functor's member's argument type for use within your template? The following is a use of this mythical functionality:

template < typename FunctorType >
bool doIt( FunctorType functor, typename FunctorType::operator()::arg1 arg )
{
    return functor( arg );
}

是否有一个有效的语法来代替我的神话 FunctorType :: operator（）:: arg1 ？

Is there a valid syntax that would substitute for my mythical FunctorType::operator()::arg1 ?

推荐答案

最简单的方法是要求你的函数为参数类型提供一个 typedef ，或引入一个traits类。

No there is not. The most elegant way to do this would be to either require your functors to provide a typedef for the argument-type, or to introduce a traits-class. The latter is useful if you want your template to work with functors and functions.

或者，您可以让参数类型为第二个模板参数：

Alternatively, you can just make the argument type a second template parameter:

template < typename FunctorType, class ArgumentType >
bool doIt( FunctorType functor, ArgumentType arg )
{
    return functor( arg );
}

编译器仍然会提出 ArgumentType 与函子所需的类型不匹配。

The compiler will still complain if ArgumentType does not match the type required by the functor.

这篇关于是否可以从（Functor成员的）函数签名中检索参数类型以在模板中使用？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！