From: David Vallner <david@...>
Date: 2006-02-07T08:41:57+09:00
Subject: Re: Creating classes only when needed?

Dňa Utorok 07 Február 2006 00:30 Paatsch, Bernd napísal:
> Hello,
>
> I am fairly new to ruby and need some help
> I am structuring my code using classes.
> The application I work on requires input data. This data may require all or
> some of the classes I create. Instead of having a section in the main code
> creating all classes I would like to create only those classes that I need
> while reading the data. However I do not know how to do that. Below is the
> outline of my code.
>
> Any suggestions
>
>  class ReadFileFactory
> # handles calling the right class to for reading the data
> # from database, from CSV-file, etc.
>  ... code goes here .....
>  end
>
>   class CSVReadFile( externalClass, nameID )
> # handles reading data using a csv-file and assigning it to the appropriate
> Hash
>  ... code goes here .....
>     case signal
>     when  nameID
>       externalClass.getLine(tempStore)
>    when ....
>   end
>
>   class AddSubscriber
> # handles adding a subscriber
>  ... code goes here .....
>   end
>
>
> # main program
>
> # Initialize I don't like that
>  class1 = Class1.new;
>  class2 = Class2.new; #etc
>  test =  ReadFileFactory.start_csv_readfile("sample.csv")
>
> test.processingFile( class1 )
>
> # I rather would have something like that
> ReadFileFactory.start_csv_readfile("sample.csv") will return only the
> classes I need.

Well, your example is fairly generic, so I'll be guessing what you really want 
to do.

I think you started on the right track with the factory. If I understand you 
right, that one provides an adapter for the way the data is stored. You could 
continue by storing the data type in the adapter, or whatever it returns, and 
then processing it into some sort of facade processing class that will 
internally decide what processing is required for what data and hide this 
from the "main" script body.

David Vallner
Might be horribly, horribly wrong