From: Chris Morris <home@...>
Date: 2002-05-20T02:22:19+09:00
Subject: RE: Object <-> Relational mapping

> db.select_all(long_sql_statement) do |row|
>         foo = Foo.new
>         foo.a = row['a']
>         foo.b = row['b'].to_i
>         foo.c = row['c'].to_f
>         #...
>         foo.z = row['z']
> end

Some possible improvements. I'd try to take advantage of .send - so the loop
would be something like:

... do |row|
  # row would need to be a hash
  row.each do |colname, colvalue|
    foo.send('=' + colname, colvalue)
  end
end

As far as handling row['b'].to_i, etc. -- if it has translate types, make
that transformation in the set accessor method of foo's class.

For a C# app I'm working, I use reflection to do a similar thing as the row
loop above (although it ain't nearly so clean :). In addition, to write the
C# classes that front the objects, I wrote a Ruby script that uses Ruby\ODBC
to read all the column info out of a table and automatically write the C#
class. It's not fully automated, but it saves on a lot of typing. You could
probably do the same for Ruby classes (including automatically coding for
translations from string to the actual column datatype).

I don't know of any generic mapping lib efforts -- but I'd probably be able
to contribute some as needs arise at work.

Chris