How do I pass a TForm (this) generically?

I have two almost identical forms (Form4 and Form5) that have several common items but handle different data. I am trying to write a helper function that will take either of these forms.

Both forms are created dynamically.

So far I am able to write the function that processes the data from Form4 [Process(TForm4 *F)]. I cannot do the same from Form5 because the helper function is specific to TForm4.

From Form4

 Edit1Exit(Tobject *Sender){     
   Process(this);
 }

From Form5

 Edit1Exit(Tobject *Sender){     
   Process(this);
 }

 Process(TForm4 *F){
  // Do something like F->BitBtn1->Visible=false;
  }

The problem is that Process( ) is written for TForm4 so it won't accept TForm5.

How do I declare Process() so that it will take either form.

In general, you will have three options:

1. Write an explicit overload for each version, and duplicate the code. I.e.,

void Process(TForm4* F) {
   /// do things
}

void Process(TForm5* F) {
   /// do things
}

2. Derive from a common base class that declares a virtual interface, i.e.,

class TFormBase {
    // common virtual interface, and a virtual destructor
};

class TForm4 : public TFormBase {
    // implementation of the interface + data members
};

class TForm5 : public TFormBase {
    // implementation of the interface + data members
};

void Process(TFormBase* F) {
    // interact with F via the virtual interface
}

3. Use templates (but in that case, the implementation of your function has to be accessible where it is used; usually that means it has to live in the header file or in a file that can be included directly), i.e.,

template<typename T>
void Process(T* F) {
    // interact with the classes; assumes a common interface
}

For simplicity, I've omitted a lot of details, but this should get you started.