Pointers to Member Functions

I have a table where one of the items is a pointer to member function, e.g.:

class State : public QObject {
QOBJECT
public:
State() {}
~State() {}
int Set_State (uint Object, int New_State);
int Validate_State(int New_State);
};

typedef int (State::* pState_Valid)(int Requested_State);

struct {
int Current_State;
pState_Valid pValidator;
} State_Tbl[] = {
0, &State::Validate_State,
1, &State::Validate_State
};

int State::Validate_State(int Requested_State) {
int Validated_State;
...
return(Validated_State);
}

int State::Set_State(uint Object, int Requested_State) {
int Validated_State;

Validated_State = (*State_Tbl[Object].pValidate_State)(Requested_State);
...
return(Validated_State);
}

The error I get (gnu compiler) on the line that's calling the member function is:

error: invalid use of 'unary*' on pointer to member

What am I doing wrong?

Thanks,
Doug Broadwell

Use this instead:
Validated_State = (State_Tbl[Object].*pValidate_State)(Requested_State);

You were not dereferencing the function, but the struct object.
Try dereferencing the function pointer, which is the correct way.

Regards

Thanks Marcel, that fixed that error. Now I'm getting the error:

'pValidator' undeclared (first use this function)

?????
Help again.

on which line in the code this error comes?

The error is on this line:

Validated_State = (*State_Tbl[Object].pValidate_State)(Requested_State);

Doug

Quote:

---

Originally Posted by Doug Broadwell

The error is on this line:

Validated_State = (*State_Tbl[Object].pValidate_State)(Requested_State);

Doug

---

But that is the same code you had before when you started the thread...:confused:

Validated_State = (State_Tbl[Object].*pValidate_State)(Requested_State);

Who is pValidate_State?
You should call (State_Tbl[Object].*pValidator)(Requested_State);, because pValidator points to State::Validate_State.

What is the point of pointers to functions if you will call the functions directly?

Oops, you're right, the actual line that is generating the error is the edited one:

Validated_State = (State_Tbl[Object].*pValidator)(Requested_State);

My mistake in copying/simplifying the code and having 'pValidate_State' instead of the correct 'pValidator' here. It still gets the 'pValidator undeclared' error.

Doug

Just realized one problem, I haven't instantiated any State objects yet to point to!

My newbe status reveals itself yet again.

Doug