Passing pointers to function into another function

[acerunner316]

so i have to specify in the argument list of 'ManageTasks' to expect a member function and not a regular function? How do I do that?

[David Crow]

The methods FunctTask1(), FunctTask2(), FunctTask3() either need to be static or not a member of CModule.

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"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

[Mark Salsbery]

In addition to DavidCrow's reply.... You can pass pointers to member functions but to use them you have to have an object of the class they are a member of, just like any class method call. Mark

Mark Salsbery Microsoft MVP - Visual C++ :java:

[acerunner316]

In that case, I can't use it the way I had intended. I need FunctTask1,2,&3 to be able to access other member variables and functions that aren't static, so making it static wont work. Time to rethink. Thanks for the help.

[Lost User]

typedef unsigned char (CModule::*FUNCPTR)(unsigned char,unsigned char);
ManageTask(1,1,&CModule::FunctTask1);

[acerunner316]

tried that, but when I call ptrFunct(0,0); from inside ManageTask, I get an error saying "term does not evaluate to a function". Edit: nevermind. just realized i have to call it like this: (this->*ptrFunct)(0,0); -- modified at 18:42 Thursday 1st November, 2007

[David Crow]

acerunner316 wrote:

I need FunctTask1,2,&3 to be able to access other member variables and functions that aren't static, so making it static wont work.

You're not out of luck just yet. Two plausible solutions still exist. One is to change the third parameter of ManageTasks() to include CModule. I don't have the syntax readily available, but it's not uncommon and can easily be searched. The other would be to create two versions of FunctTask1(), FunctTask2(), and FunctTask3(). One would be static and the other would not. That would look something like:

BYTE CModule::FunctTask1(BYTE Param1, BYTE Param2)
{
// access CModule variables and functions
}

static BYTE CModule::FunctTask1(BYTE Param1, BYTE Param2, CModule *pThis )
{
// call the non-static version
return pThis->FunctTask1(Param1, Param2);
}

void CModule::ManageTasks(BYTE Param1, BYTE Param2, BYTE (*ptrFunct)(BYTE, BYTE), CModule *pThis )
{
... //unrelated code removed
switch (ptrFunction(1, 1, pThis))
{
case 0: // handle results
case 1: // handle results
}

... //unrelated code removed

}

void CModule::OnSelchangeCombobox()
{
switch(m_Combobox->GetCurSel())
{
case 0: ManageTask(1, 1, FunctTask1, this); break;
case 1: ManageTask(1, 1, FunctTask2, this); break;
case 2: ManageTask(1, 1, FunctTask3, this); break;
}
}

---

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

[acerunner316]

DavidCrow wrote:

You're not out of luck just yet. Two plausible solutions still exist. One is to change the third parameter of ManageTasks() to include CModule. I don't have the syntax readily available, but it's not uncommon and can easily be searched.

Tried that, see by reply to Randor below. I will try the overloaded function way. However, one of the reason I wrote my code the way it is was so that I can easily add more functions later (ie FunctTask4,5,6 etc) without having to change much code. Just add a new case in the OnSelchangeCombobox function. I can still call ManageTask to do the same things. Having to overload every single one seems inefficient to me.

[Stephen Hewitt]

Modify the class as follows:

CModule : public CDialog
{
// Construction
public:
   CModule (CWnd* pParent = NULL); // standard constructor
...
private:
   unsigned char FunctTask1(unsigned char, unsigned char);
   unsigned char FunctTask2(unsigned char, unsigned char);
   unsigned char FunctTask3(unsigned char, unsigned char);
   typedef unsigned char (CModule::*PFunctTask_t)(unsigned char, unsigned char);
   void ManageTasks(unsigned char, unsigned char, PFunctTask_t);
};

void CModule ::ManageTasks(unsigned char Param1, unsigned char Param2, unsigned char (*ptrFunct)(unsigned char, unsigned char)
{
   ... //unrelated code removed

switch ((this->*ptrFunction)(1,1))
   {
   case 0:
      //handle results
   case 1:
      //handle results
   }

... //unrelated code removed
}

And modify the calls like this:

void CModule::OnSelchangeCombobox()
{
   switch(m_Combobox->GetCurSel())
   {
   case 0: ManageTask(1, 1, &CModule::FunctTask1); break;
   case 1: ManageTask(1, 1, &CModule::FunctTask2); break;
   case 2: ManageTask(1, 1, &CModule::FunctTask3); break;
   }
}

-- modified at 20:49 Thursday 1st November, 2007

Steve

[David Crow]

acerunner316 wrote:

Having to overload every single one seems inefficient to me.

Indeed, I was just offering all the possibilities I could think of, and let you figure out which one would be best for your situation.

---

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne