std::function
提供了我提出的解决方案的大多数构建块。
这是我建议的解决方案。
#include <iostream>#include <functional>//-------------------------------// BEGIN decorator implementation//-------------------------------template <class> struct Decorator;template <class R, class... Args>struct Decorator<R(Args ...)>{ Decorator(std::function<R(Args ...)> f) : f_(f) {} R operator()(Args ... args) { std::cout << "Calling the decorated function.n"; return f_(args...); } std::function<R(Args ...)> f_;};template<class R, class... Args>Decorator<R(Args...)> makeDecorator(R (*f)(Args ...)){ return Decorator<R(Args...)>(std::function<R(Args...)>(f));}//-------------------------------// END decorator implementation//-------------------------------//-------------------------------// Sample functions to decorate.//-------------------------------// Proposed solution doesn't work with default values.// int decorated1(int a, float b = 0)int decorated1(int a, float b){ std::cout << "a = " << a << ", b = " << b << std::endl; return 0;}void decorated2(int a){ std::cout << "a = " << a << std::endl;}int main(){ auto method1 = makeDecorator(decorated1); method1(10, 30.3); auto method2 = makeDecorator(decorated2); method2(10);}输出：
Calling the decorated function.a = 10, b = 30.3Calling the decorated function.a = 10
ps
Decorator提供了一个可以进行功能调用以外的其他功能的地方。如果您想简单地传递至
std::function，可以使用：
template<class R, class... Args >std::function<R(Args...)> makeDecorator(R (*f)(Args ...)){ return std::function<R(Args...)>(f);}
