CODEWITHSUNDEEP
c++
Anupama Pathirage
Anupama Pathirage

Reputation: 691

C++ Passing a pointer to a member function as an argument

I need to pass a pointer to a member function as an argument to a member function in another class. What I'm doing is something like below. I want to call int Processor::AddJob(void (_pFunc)(void*), void* _pArg) method with void* ProcessHandler::Task(void* a) as the first argument. I did it as 

TaskFunc pFunc1 = &ProcessHandler::Task;
p_Processor->AddJob(pFunc1,10);

But it gives the error

error: no matching function for call to Processor::AddJob(void* (ProcessHandler::&)(void), int)’ Processor.h:47: note: candidates are: int Processor::AddJob(void* ()(void), void*)

Can someone please help me on this.My implementation is as follows.(Not the exact code-it is much larger than this)

class Processor 
{
public:
    Processor();
    virtual ~Processor();

    int AddJob(void *(*_pFunc)(void*), void* _pArg);
};

int Processor::AddJob(void *(*_pFunc)(void*), void* _pArg)
{
    //Job addition related code goes here
}


/////////////////////////////////////////////////////////////////////////////
typedef void* (ProcessHandler::*TaskFunc)(void*); 
class ProcessHandler
{
public:
    ProcessHandler(Processor* _pProcessor);
    virtual ~ProcessHandler();
    void* Task(void* a);
    void Init();

private:
    Processor* p_Processor;
};


void* ProcessHandler::Task(void* a)
{
    //Task related code goes here
}

void ProcessHandler::Init()
{
    TaskFunc pFunc1 = &ProcessHandler::Task;
    p_Processor->AddJob(pFunc1,10); //This give the compile error.
}

/////////////////////////////////////////////////////////////////////////
int main()
{
    Processor* pProcessor = new Processor();
    ProcessHandler* pProcessHandler = new ProcessHandler(pProcessor);
    pProcessHandler->Init();
}

Upvotes: 1

Views: 395

Answers (3)

ATaylor
ATaylor

Reputation: 2598

void (_pFunc)(void*) is a C-Function pointer, and as such, you can only either pass C-Functions via that pointer, or static functions.

void (ProcessHandler::*)(void); //Since you already have a Typedef, pass that as 'type'

should help you call a member function. Call it with the pointer to member function calling syntax:

(objectPointer->*functionPointer)();

Upvotes: 0

KAction
KAction

Reputation: 2017

In C++ I would suggest to do_NOT use pointers to functions(raw pointers are arguable too). You should use std::function(boost::function) for more generality, or template. Latter gives you a bit perfomance, but less typecheck.

Upvotes: 1

ThirdOne
ThirdOne

Reputation: 1248

You can only pass static member functions via the address-of operator. Regular member functions don't work. You should consider using std::function.

Upvotes: 3

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