C++ Callback function pointer

Question

i'm trying to create a callback function in Cocos2d-X. I have a singleton class (AdsMgr). In the AdsMgr, i want to store the function pointer. How should i replace the callBackPauseResume with the passing in parameter?

AdsMgr.h

class AdsMgr
{
private:
    static bool isAdsEnabled();

public:
    static void(*callBackPauseResume)(int index);
    static void initAds(void(*incallback)(int index));
}

AdsMgr.mm

void AdsMgr::initAds(void(*incallback)(int index))
{
    callBackPauseResume = incallback;

//    incallback(1);
}

MainScene.cpp

if(btn4 && btn4->getBoundingBox().containsPoint(location))
{            
     CCLOG("SHOW INTERSTITIAL");
     AdsMgr::initAds(MainScene::pauseResumeDuringAds);
}

void MainScene::pauseResumeDuringAds(int inFlag)
{
    switch (inFlag) {
        case 0:
        // Pause game
            break;
        case 1:
            // Resume Game
            break;
        default:
            break;
    }
}

I'm unable to compile and encountered the following errors:

Undefined symbols for architecture arm64:
  "AdsMgr::callBackPauseResume", referenced from:
      AdsMgr::initAds(void (*)(int)) in AdsMgr.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Answer 1

Judging by your compile error, you haven't defined your callBackPauseResume variable. That's what the error is saying.

In addition to its declaration inside the class, you also need to add a definition for it, outside the class, in AdsMgr.mm:

void (*AdsMgr::callBackPauseResume)(int) = nullptr;