From: Tom Sawyer <transami@...>
Date: 2002-09-03T15:42:47+09:00
Subject: Re: Idea: Ruby Object Persistence Service


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On Mon, 2002-09-02 at 18:48, Holden Glova wrote:
> I have never heard of DBize before, does this maintain mappings of collec=
tions=20
> for you as well? The holy grail is to not write SQL (or whatever you need=
 to=20
> store persistently) for the majority of the cases.

well, if i understand you correctly, then yes. DBize includes two mixins
actually, DBize::Record and DBize::Subrecords. If you subclass Array and
mixin DBize::Subrecords, the you have a means of dealing with a
collection of objects mapped to the database. if, like i said, that is
what you mean by "mappings of collections"

indeed, no sql required, in all cases i think.

essentially DBize knows the meta-inforamation of the table your object
pertains too. so it uses the dynamicism of ruby to make method calls
using #send with the table's attribute (field) names. for instance,
here's a mockup:

CREATE TABLE mapped_table
  ( record     SERIAL PRIMARY KEY,
    name       text DEFAULT '',
    value      text DEFAULT ''
  );

class MappedObject
  include DBize::Record =20
  attr_accessor :record =20
  attr_accessor :name
  attr_accessor :value
  def table
    'mapped_table'
  end =20
end

mo =3D MappedObject.new
mo.load_from_database(1)
mo.name=3D"A New Name"
mo.update_database

this loads the record for mapped_table where record=3D1 into the object.
changes the name attribute and saves it back to the table.

notice the database atrributes (fields) and the object accessor
attributes have the exact same names. this is really the key to DBizes
ease of use. and is not limiting since you can always define accessor
methods by hand, even complex ones.

the record attribute is required by DBize to get the record's id
attribute. if that field isn't called record in the table then simply
define record manually to access whatever it is:

  attr_accessor :myid

  def record
    myid
  end

  def record=3D(x)
    myid =3D x
  end

i'll probably improve on this in the future. the method #table is
required as well, to tell DBize which table the object is stored in,
this i beleive i am in the process of moving to a class method instead.
anyway you get the idea.

--=20
tom sawyer, aka transami
transami@transami.net

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