OpenEuphoria

Introducing Quartz

• Posted by Roderick Jackson <rjackson at CSIWEB.COM> Feb 19, 1999
• 400 views

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Hi all,

With the help of a few folks from the list, I've been able to complete =
my contribution to the Euphoria community... I call it Quartz.

Quartz is a library of routines to emulate object-orientation and =
classes in Euphoria. I understand that there have been at least two =
other such libraries created already; I'm not trying to imitate them =
(I'm not sure what features they have), but just to provide something =
simple and easy to use, something that fits what I feel is a logical way =
to implement the concept.

Quartz allows q-objects to be derived from user-defined classes, either =
based on a foundational class "qobject", or on a previously-defined =
class. Classes inherit data members as well as methods from parent =
classes (although methods can be overwritten in subclasses). Constructor =
methods are supported as well, but not deconstructors. Classes, members =
and methods are labeled and accessed via their names (Euphoria =
"strings"). Finally, error checking is performed, and a few global types =
and constants are provided to aid use of the library.

There are five major Quartz routines:

   define_qclass (..) - this sets up the structure for each class. Class =
name, parent it inherits from, member names, method names, the routine =
IDs of method functions, and the routine ID of the constructor function =
(else NO_CONSTRUCTOR) are set here. If your classes are all in a =
seperate file, simply "include quartz.e" at the top, detail the method =
functions, then use a call to "define_qclass" for each. Then in your =
main program, just include your class file.

   new_qobject (class, param) - this returns a new q-object, of the =
specified class. The parameter is required, but only used if the class =
has a constructor method.

   send_qmessage (qobject, method, param) - this invokes a method. Each =
method, defined by the user, is a global function accepting the q-object =
and one other parameter. An method which an q-object inherits will =
always be able to properly manipulate that q-object, provided that =
"get_qmember" and "set_qmember" are used, and that related methods =
haven't been overwritten.

   get_qmember (qobject, member) - this returns the value of a =
q-object's specified member. For example: W =3D get_qmember (MyCat, =
"Weight").

   set_qmember (qobject, member, value) - this returns the q-object, =
modified so that it's specified member is set to the new value. For =
example: MyDog =3D set_qmember (MyDog, "LifeStatus", DEAD). To emulate =
encapsulation, use only in method code.

In addition, two minor functions have been provided that may be of use:

   get_qobject_class (qobject) - returns the Euphoria "string" naming =
the object's class.

   is_qsubclass (class, class) - returns TRUE if the first class is a =
direct or indirect subclass of the second.

This is not a full public release yet, although please feel free to try =
out and make use of the library. I've done some testing, but I want to =
work on more thorough documentation and a better example program before =
I submit Quartz for posting on the Euphoria site--optimizing the code =
also has yet to be done. The Quartz library (quartz.e), the example =
program (example.ex) and the include file created for the example =
(animals.e) are attached. Quartz runs under Euphoria 2.0 and 2.1, I =
haven't tested it with anything below that.

I'd appreciate any comments on Quartz. And again, thanks for the help, =
and enjoy! 


Rod Jackson



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