OpenEuphoria

RE: Euphoria being OO Survey.

• Posted by Matt Lewis <matthewwalkerlewis at yahoo.com> May 16, 2003
• 639 views

> From: fred at jordah.freeserve.co.uk [mailto:fred at jordah.freeserve.co.uk]
> > Matt wrote:

> Matt, think of it this way. You are attempting to write a 
> cross-platform GUI library.  To make this library readily 
> cross-platform you'll have to code your own widgets...eg lists,menus
> 
> With time you go to look at all your widgets and see a lot of 
> repeated code, then u have to clean it up. Clean up ends up 
> introducing bugs, with time, u go to notice that it gets
> annoying trying to modularise your code as it grows
> bigger...etc. With OO, i would create simply a class with eg default
> properties,virtual functions,methods. Say, CWnd Class like in 
> MFC, then to all other controls eg when coding the button class. i would 
> simply create a class that inherits from the CWnd class, then overide
certain 
> methods and have a button control.

Well, frankly, this is an example of a poor engineering process (which I am
often guilty of following).  There's no reason why you had to repeat a lot
of code.  Some planning up front could have saved that effort.  I've found
that over time I've gotten better at the up front planning (a big part of
which is making a conscious decision to do so), and it's a tremendous help.
I've heard many say that OO ("properly" done) often requires *more* up front
design work.

> I dunno how to explain it since i'm not an experienced OO 
> user but i think u get what i'm getting at...(i think polymophism).
> Anyway, have u used MFC? See how easy it is? what is better, 
> is that, coding ur custom controls is simply involves extending certain 
> classes eg CWnd

Have not, and probably will never use MFC.  In any case, this is really not
unlike the process of extending, say, win32lib (of which I've done quite a
bit).  When I added ListViews and TreeViews, I didn't have to write a whole
new slew of functions that duplicated other things.  I simply extended what
was already there and appropriate to the task, and added new functionality
that didn't exist (dealing with ImageLists, for instance).

> Another issue is when you have function names/proc names that 
> are similar but different in function...eg Incase you look at win32lib, 
> If you look at his setText() proc, u'll notice he uses the if switch 
> lots to adjust for it to work for  different controls eg
> If class=Menu then
> --code here
> elsif class = window then
> --code here
> end if
> 
> wouldn't it be easier to do
> eg in java
> JFrame mw = new JFrame();
> JMenu me = new JMenu();
> mw.setText("blah");
> me.setText("xxg");
> mw.setVisible(1);

How is the java example easier than the following?

constant
mw = create( JFrame ),
me = create( JMenu )
setText( mw, "blah" )
setText( me, "xxg" )
setVisible( mw, 1 ) 

>From the library standpoint, why is the if switch so wrong?  It simply
brings the code to one place, which is probably a plus for maintenance.
Also, many of the functions in win32lib end up sending a very similar
message to some control, but having all of it in one place simplifies things
a bit (e.g., only need to allocate a string in one place).

If you don't like the if switch, you can use routine_id() to add arbitrarily
large numbers of routines (which can, of course, be located anywhere) using
an associative list:

ix = find( control_type, valid_control_types )
call_proc( control_routines[ix], {})

Matt Lewis