One-liner for RAII on non pointer?

Question

Related topic

std::unique_ptr, deleters and the Win32 API

To use a Win32 Handle as a RAII, I can use the following line

std:         


        

Answer 1

I often use this in C++11:

 #include 

 namespace{
    template
    struct RAII_Helper{
        template
        RAII_Helper(InitFunction &&init, F &&exit) : f_(std::forward(exit)), canceled(false){
            init();
        }
        RAII_Helper(F &&f) : f_(f), canceled(false){
        }
        ~RAII_Helper(){
            if (!canceled)
                f_();
        }
        void cancel(){
            canceled = true;
        }
    private:
        F f_;
        bool canceled;
    };
 }
 template
 RAII_Helper RAII_do(F &&f){
    return RAII_Helper(std::forward(f));
 }

 template
 RAII_Helper RAII_do(Init &&init, Exit &&exit){
    return RAII_Helper(std::forward(init), std::forward(exit));
 }

usage:

FILE *f = fopen("file", "r");
if (!f)
    return "error";
auto filecloser = RAII_do([=]{fclose(f);});

//also makes for good init / exit objects
static auto initExit = RAII_do([]{initializeLibrary();}, []{exitLibrary();});

I like it because it works for arbitrary code, not just pointers or handles. Also the cancel function could be omitted if never used.