On Tue, 26 Sep 2000, Angus Leeming wrote:
[...]
> Angus> Finally, I have made the xforms implementation of FormCopyright a
> Angus> derived class of FormBase and demonstrated that none of these
> Angus> FormXXX classes need be dependent on Dialogs.h if they are
> Angus> passed pointers to the relevant show, hide and update signals
> Angus> directly by Dialogs.C.
>
> Allan> I don't like the looks of this much at all...
>
> All fair comment. I was, however, merely trying to demonstrate that it's
> possible to have one base class that does all this rather nasty stuff. I was
But one base class shouldn't be trying to second guess what it's derived
classes are going to be doing.
> thinking last night that the production code would merely need a flag
> definining whether the browser was invariant across all buffers and therefore
> needed a hideAll signal, or was buffer dependent and therefore required the
> hideBufferDependent, updateBufferDependent signals.
Just add these lines to FormBase:
/// Derived classes setup signal connections
virtual void connect() = 0;
/// Derived classes disconnect signal connections
virtual void disconnect() = 0;
That way all connections are handled by the derived classes. You could
alternatively define empty functions so that derived classes that don't
need extra connections aren't required to implement them but that's more a
matter of style since no-one is going to create an instance of a FormBase.
The stuff that's common (or more specifically identical) between the
derived classes can go into FormBase. The distinct features of the
derived classes belong in derived classes. If you try to keep pointers to
the various signals each different dialog might want to connect you either
restrict everything to only one update and one hide signal (and possibly
just one show signal) or you have to keep adding extra signals just so you
can support some new dialog but such a change would mean recompiling every
form anyway (the thing you were originally trying to avoid!).
> Same idea as your's for the form property mask.
Good.
> Allan> Anytime someone decides to add an extra signal for a dialog they
> Allan> have to change Dialogs.C and FormXxxx.[Ch] instead of just
> Allan> FormXxxx.C (assuming the signal exists or Dialogs.h also if the
> Allan> signal doesn't).
>
> Again, good point. As I was saying, I was just playing! With reflection, the
> present interface is clean and simple. Think of this submission as a
> work-in-progress, evolving thought experiment!
>
> IF I can make a neat, elegant interface to FormBase, then I definitely think
> we gain. The resultant daughter classes are immeasurably simpler. Have you
> seen FormCopyright??? Anyway, I'll press ahead and show you my vision!
We gain a lot already with the existing FormBase. Not much else to fiddle
with IMO -- apart from the stuff above. You're doing well so far. But if
you find time do some testing and bug fixing we've really got to get 1.1.6
sorted.
Allan. (ARRae)
