[Pharo-project] [squeak-dev] Proper Smalltalk lots of classes

Jan van de Sandt jvdsandt at gmail.com
Sat Jan 1 11:18:34 EST 2011


Hello Jimmie,

I had to do something similar a while ago. I had to support a complex XML
schema for a standard message format of the Dutch government (StUF).

The Java implementation used JAXB to generate a few thousand data objects.
Very clumsy.

In Smalltalk I made some code to generate Magritte descriptions for all the
structure and field definitions in the XML schema. Using the Magritte
descriptions it was very easy to read and write messages in the correct
format. I created real classes only for the few message types that required
some logic. For all the other message types I used some generic class that
stores the values in a dictionary.

So my advice is to have a look at Magritte. It can help you handle the type
information without creating/generating lots of classes.

Jan.



On Fri, Dec 31, 2010 at 11:24 PM, Jimmie Houchin <jlhouchin at gmail.com>wrote:

> Hello,
>
> I am porting the FIX protocol to Squeak/Pharo.
> http://www.fixprotocol.org/
>
> It is the Financial Information eXchange protocol. It is used by many firms
> in the financial industries, stocks, forex, etc.
>
> There is good documentation and also a semi-reference implementation in
> Java.
> http://www.quickfixj.org
>
> I have a partial port started but I wanted a check with those who know more
> than I about proper Smalltalk coding.
>
> In the Java implementation there are over 2000 classes. In the protocol
> there are approximately 90 message types and 956 field types.
>
> I am initially creating the message classes as they form the basis of the
> protocol and the fields are simply instance variables and methods in the
> message classes.
>
> I am not porting the Java library. I am implementing the protocol in
> Smalltalk from the documentation.
>
> Initially I have created a Fix44Field class with its necessary variables.
> There are several versions of the Protocol and FIX 4.4 is the one required
> for my application.
>
> With this Fix44Field class I am creating a Dictionary with the 956
> different field types. I am planning on creating a constructor method which
> will create the desired field from the information in the dictionary about
> the field and its properties.
>
> Am I way off base here? Should I really create the 956 classes necessary to
> for each field in addition to the 90 or so message classes, and then I don't
> know what else I haven't discovered yet. Having 1000+ classes just seems
> unwieldy and naively it just doesn't feel like the Smalltalk way. I could be
> wrong, but I haven't seen such an example to my memory. I don't know enough
> about Java to know if it is good Java form either.
>
> When I have a reasonably fleshed out, tested and working solution, I will
> make the source available under a MIT license. I would love to see
> Squeak/Pharo become an out of the box viable option for trading
> applications.
>
> Advise and wisdom greatly appreciated.
>
> Thanks.
>
> Jimmie
>
>
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