From: David.Stagner@... Date: 2002-09-21T00:04:55+09:00 Subject: Re: Mapping Db Fields to Class Attributes This is a multipart message in MIME format. --=_alternative 00529FF586256C3A_= Content-Type: text/plain; charset="us-ascii" Depends on how complex your code is. I tried doing this once in Java, to deal with really atrocious field names in the database (as far as i could tell, their basic naming scheme was to remove all vowels except the silent ones, but it was about as consistent as English). That idea went out the window when i found myself trying to create objects that had over 300 fields! (the relational design was no better than the naming scheme). I wound up just using their icky names. One thing i CAN tell you is to write a code generator to read the table DDLs and crank out wrapper classes that way (as the Pragmatic Programmers would tell you, too). If you want to map better variable names over the original database names, write them up as text metadata and feed that into your code generator. But... The bigger problem i've always encountered on sufficiently complex data is the "object-relational impedance mismatch", in which the difference between a good object model and a good relational model for the same problem is enough to make things awkward. There is lots of good discussion of this problem on the C2 wiki and elsewhere on the web. "Matthew, Graeme" 09/19/02 05:59 PM Please respond to ruby-talk To: ruby-talk@ruby-lang.org (ruby-talk ML) cc: Subject: Mapping Db Fields to Class Attributes Hi All, thanks who helped me yesterday ... I am currently designing my "object model" for a project management system for software projects. One problem I have always encountered irrespective of wehter the language is Perl, Python or Ruby is the mapping of database fields to class attributes. For example if I do a mysql db call and load a hash for a specific tuple, in most cases the db table names will not be in user firendly naming format eg prj_acc_id or prj_name, it would be silly to use these names as accesor's in a class. Has anyone come up with an easy yet effective way of doing this ? I was thinking of having a corresponding hash that mapped the field name to the attribute name I looked at ruby's alias option but am not sure if this is the appropriate item to use as an alternative to hash mapping ? Any advice would be most welcome Graeme Matthew Analyst Programmer Mercer Investment Consulting Level 29, 101 Collins Street, Melbourne, VIC, 3001, Australia Tel - 61 3 9245 5352 Fax - 61 3 9245 5330 visit http://www.merceric.com __ ********************************************** This e-mail and any attachments may be confidential or legally privileged. If you received this message in error or are not the intended recipient, you should destroy the e-mail message and any attachments or copies, and you are prohibited from retaining, distributing, disclosing or using any information contained herein. Please inform us of the erroneous delivery by return e-mail. Thank you for your cooperation. ********************************************** ec03/04 --=_alternative 00529FF586256C3A_= Content-Type: text/html; charset="us-ascii"
Depends on how complex your code is.  I tried doing this once in Java, to deal with really atrocious field names in the database (as far as i could tell, their basic naming scheme was to remove all vowels except the silent ones, but it was about as consistent as English).  That idea went out the window when i found myself trying to create objects that had over 300 fields! (the relational design was no better than the naming scheme).  I wound up just using their icky names.

One thing i CAN tell you is to write a code generator to read the table DDLs and crank out wrapper classes that way (as the Pragmatic Programmers would tell you, too).  If you want to map better variable names over the original database names, write them up as text metadata and feed that into your code generator.  But... The bigger problem i've always encountered on sufficiently complex data is the "object-relational impedance mismatch", in which the difference between a good object model and a good relational model for the same problem is enough to make things awkward.  There is lots of good discussion of this problem on the C2 wiki and elsewhere on the web.



"Matthew, Graeme" <Graeme.Matthew@mercer.com>

09/19/02 05:59 PM
Please respond to ruby-talk

       
        To:        ruby-talk@ruby-lang.org (ruby-talk ML)
        cc:        
        Subject:        Mapping Db Fields to Class Attributes


Hi All, thanks who helped me yesterday ...


I am currently designing my "object model" for a project management system
for software projects. One problem I have always encountered irrespective of
wehter the language is Perl, Python or Ruby is the mapping of database
fields to class attributes. For example if I do a mysql db call and load a
hash for a specific tuple, in most cases the db table names will not be in
user firendly naming format eg prj_acc_id or prj_name, it would be silly to
use these names as accesor's in a class.

Has anyone come up with an easy yet effective way of doing this ? I was
thinking of having a corresponding hash that mapped the field name to the
attribute name

I looked at ruby's alias option but am not sure if this is the appropriate
item to use as an alternative to hash mapping ?

Any advice would be most welcome

Graeme Matthew
Analyst Programmer
Mercer Investment Consulting
Level 29, 101 Collins Street, Melbourne, VIC, 3001, Australia
Tel  - 61 3 9245 5352 Fax - 61 3 9245 5330
visit http://www.merceric.com

__


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If you received this message in error or are not the intended recipient, you
should destroy the e-mail message and any attachments or copies, and you are
prohibited from retaining, distributing, disclosing or using any information
contained herein.  Please inform us of the erroneous delivery by return
e-mail.

Thank you for your cooperation.
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