Construct std::function with a constructor based on template

问题

Is it possible to construct a std::function with the constructor of a type defined by a template argument?

For example:

template <typename T>
bool registerType()
{
    const std::function<T()> func = &T::T; //I know this doesn't work
    //...
}

回答1:

I don't think so, because constructors don't have names, you can't take a pointer/reference to them, and in general they don't behave quite like functions.

You could use a lambda to initialize a std::function with the same signature:

const std::function<T()> func = [](void) { return T(); } // or something like that

Calling it produces the same result as using the expression T() to construct a temporary of type T, but possibly with different side-effects. In the case of a true function call there's an extra temporary in the return statement, which nominally is copied/moved to the return value. The implementation may or may not elide the extra temporary.

来源：https://stackoverflow.com/questions/12386725/construct-stdfunction-with-a-constructor-based-on-template