From: avi@...4.com (Avi Bryant)
Date: 2002-05-20T08:48:39+09:00
Subject: Re: Object <-> Relational mapping

Thomas Hurst <tom.hurst@clara.net> wrote in message news:<20020519165132.GA52065@voi.aagh.net>...
> I'm getting very, very tired of writing code that looks like this:
> 
> 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
> 
> It gets even worse when you get relations etc to worry about.
> 
> I've heard of at least two mentions of people writing object-relational
> mappers, and I'm sure plenty of you lot have written db heavy apps.

I played with OR mapping in Ruby a long time ago, but mostly just as
an experiment.  You might find something of interest in my code, which
I think is still available at http://beta4.com/kansas.tgz (it assumes
MySQL - I think Eli Green has a version of this that works with
Ruby/DBI as well).  I wouldn't expect you to be able to use it
directly, however, at least not without a fair amount of tweaking.

One of the more interesting things it did was use blocks to generate
sql queries - that is, you'd do something like

x = 'asd%'
Foo.select{|foo| (foo.a == 1) & (foo.bar.c =~ x)}

rather than

SELECT * FROM Foo, Bar
WHERE Foo.a = 1
AND Foo.bar_id = Bar.id
AND Bar.c LIKE 'asd%'.

Cheers,
Avi