函数包装模板

发表于 分类于

普通函数

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#include <utility>
#include <iostream>

template<typename Fn, Fn fn, typename... Args>
void func_wraper(Args... args)
{
    /*do some thing*/
    std::cout << "hello, ";

    fn(std::forward<Args>(args)...);

    /*do some thing*/
    std::cout << " bye.";
}

#define WRAPER(FUNC) func_wraper<decltype(&FUNC), &FUNC>

void func_a(int i){
    /*do some thing*/ std::cout<<"func_a("<<i<<")";
     }
int main(){
    WRAPER(func_a)(int(0));
    return 0;
}

输出

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hello, func_a(0) bye.

成员函数

在函数指针的使用上有区别，还有更多的类型，例如包装成员函数在类外使用

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#include <utility>
#include <iostream>

class MyClass{
public:
    typedef MyClass self;

    // declear and use in class
    template<typename Fn, Fn fn, typename... Args>
    void memberfunc_wrap_in_memberfunc(Args... args)
    {
        /*do some thing*/
        std::cout << "hello, ";

        (*this.*fn)(std::forward<Args>(args)...);

        /*do some thing*/
        std::cout << " bye.";
    }

    void memberfunc_a(int i)
    {
        /*do some thing*/ std::cout<<"memberfunc_a("<<i<<")";
    }
    
#define WRAPER(FUNC) memberfunc_wrap_in_memberfunc<decltype(&self::FUNC), &self::FUNC>
    
    void wrap_a(int i){
        WRAPER(memberfunc_a)(i);
    }
};

template<typename Fn, Fn fn, typename ClassA,typename... Args>
void wrap_memberfunc(ClassA* A, Args... args){
    /*do some thing*/
    std::cout << "hello, ";

    (*A.*fn)(std::forward<Args>(args)...);

    /*do some thing*/
    std::cout << " bye.";
}

int main(){
    MyClass a;
    a.memberfunc_wrap_in_memberfunc<void(MyClass::*)(int), &MyClass::memberfunc_a>(int(1));
    std::cout << std::endl;
    a.wrap_a(int(2));
    std::cout << std::endl;
    wrap_memberfunc<decltype(&MyClass::memberfunc_a) ,&MyClass::memberfunc_a>(&a, int(3));
    return 0;
}

输出

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hello, memberfunc_a(1) bye.
hello, memberfunc_a(2) bye.
hello, memberfunc_a(3) bye.