问题
What is the advantage of std::function<T1(T2)> over the original T1 (*)(T2)?
回答1:
std::function can hold more than function pointers, namely functors.
#include <functional>
void foo(double){}
struct foo_functor{
void operator()(float) const{}
};
int main(){
std::function<void(int)> f1(foo), f2((foo_functor()));
f1(5);
f2(6);
}
Live example on Ideone.
As the example shows, you also don't need the exact same signature, as long as they are compatible (i.e., the parameter type of std::function can be passed to the contained function / functor).
回答2:
std::function can hold function objects (including lambdas), as well as function pointers with the correct signature. So it is more versatile.
回答3:
Apart from the cleaner look and a more descriptive syntax, std::function can store any callable object:
- functions
- lambda expressions
- bind expressions
- functors
Not to mention that storing, copying, and binding objects to member functions is much easier and more intuitive.
来源：https://stackoverflow.com/questions/11352936/why-do-we-use-stdfunction-in-c-rather-than-the-original-c-function-pointer