Pointer to array of class functions

Question

I'm looking for help here.

my class

LevelEditor

has functions like this:

bool SetSingleMast(Game*, GameArea*, GameArea*, vector<IShip*>*);
bool SetDoubleMast(Game*, GameArea*, GameArea*, vector<IShip*>*);
...

In main.cpp I would like to make an array of pointers to LevelEditor object's functions. I'm doing something like this:

bool (*CreateShips[2])(Game*, GameArea*, GameArea*, vector<IShip*>*) = 
{LevelEdit->SetSingleMast, LevelEdit->SetDoubleMast, ...};

But it gives me an error:

error C2440: 'initializing' : cannot convert from 'overloaded-function' to
'bool (__cdecl *)(Game *,GameArea *,GameArea *,std::vector<_Ty> *)'
with
[
    _Ty=IShip *
]
None of the functions with this name in scope match the target type

I don't even know what does it mean. Can somebody help me?

A pointer to a function is not the same as a pointer to a member function. I recommend you read about std::function and std::bind — Some programmer dude
– Some programmer dude, Commented May 3, 2013 at 11:56
You can't have a pointer to a particular object's function, but to the class' function (method) - LevelEditor::SetSingleMast. — Luchian Grigore
– Luchian Grigore, Commented May 3, 2013 at 11:56

Mike Seymour · Accepted Answer · 2013-05-03 14:45:07Z

6

You can't use ordinary function pointers to point to non-static member functions; you need pointers-to-members instead.

bool (LevelEditor::*CreateShips[2])(Game*, GameArea*, GameArea*, vector<IShip*>*) =
{&LevelEditor::SetSingleMast, &LevelEditor::SetDoubleMast};

and you need an object or pointer to call them with:

(level_editor->*CreateShips[1])(game, area, area, ships);

although, assuming you can use C++11 (or Boost), you might find it simpler to use std::function to wrap up any kind of callable type:

using namespace std::placeholders;
std::function<bool(Game*, GameArea*, GameArea*, vector<IShip*>*)> CreateShips[2] = {
    std::bind(&LevelEditor::SetSingleMast, level_editor, _1, _2, _3, _4),
    std::bind(&LevelEditor::SetDoubleMast, level_editor, _1, _2, _3, _4)
};

CreateShips[1](game, area, area, ships);

edited May 3, 2013 at 14:45

answered May 3, 2013 at 12:00

Mike Seymour

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1 Comment

hugerth Over a year ago

Thanks a lot, I'll try this and use typedef also.

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