CODEWITHSUNDEEP
c++staticfunction-pointersargument-passing
norritt
norritt

Reputation: 355

How to pass a pointer to a static function as argument to another static function from inside a static function in C++

How to pass a pointer to a static function as argument to another static function from inside a static function, which are all inside the same class? Im using VisualStudio 2010. My code looks roughly like this:

//SomeClass.h
class SomeClass
{
    public:
        static AnotherClass* doSomething(AnotherClass*, AnotherClass*);
        static AnotherClass* doSomethingElse(AnotherClass*, AnotherClass*);

    private:
        typedef float (SomeClass::*SomeOperation)(float, float);
        static AnotherClass* apply(AnotherClass*, 
                                   AnotherClass*, 
                                   SomeOperation);

        static float SomeClass::operationA(float, float);
        static float SomeClass::operationB(float, float);
};

//SomeClass.cpp
AnotherClass* SomeClass::doSomething(AnotherClass* a, AnotherClass* b)
{
    return apply(a, b, &SomeClass::operationA);
}

AnotherClass* SomeClass::doSomethingElse(AnotherClass* a, AnotherClass* b)
{
    return apply(a, b, &SomeClass::operationB);
}

AnotherClass* apply(AnotherClass* a, 
                    AnotherClass* b, 
                    SomeOperation op)
{
    /* Some sanity checking and a lot of loop stuff which is the same
     * for all operations a, b, c ... */

}

I have tried different variants but keep getting compiler errors like:

C2664 "SomeClass::apply": conversion of parameter 3 from 'float (__cdecl *)(float, float)' in 'SomeClass::SomeOperation' not possible.

Has anyone an idea what I'm doing wrong and how to fix this?

Upvotes: 1

Views: 116

Answers (3)

barak manos
barak manos

Reputation: 30136

Change this:

private:
    typedef float (SomeClass::*SomeOperation)(float, float);

To this:

public:
    typedef float (*SomeOperation)(float, float);

Or you can simply declare typedef float (*SomeOperation)(float, float) outside the class...

Upvotes: 2

Alan Stokes
Alan Stokes

Reputation: 18964

A static member function is just a function; you don't use pointer to member syntax for it.

So instead of 

typedef float (SomeClass::*SomeOperation)(float, float);

You want

typedef float (*SomeOperation)(float, float);

And you can just pass operationA rather than &SomeClass::operationA.

Upvotes: 2

dlf
dlf

Reputation: 9383

Remove SomeClass:: from the typedef.

There are a variety of syntax errors in the example, but after fixing them and doing that, I could compile your code.

Upvotes: 0

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