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Where Plugin

UPDATE: I had to disable comments, because I was getting spammed with hundreds of “cool site” messages. Feel free to contact me in any other way.

Working with RubyOnRails is a really wonderful way of developing applications. The plugin system allows extensions without modifying the core of rails.

Here’s my second plugin: WherePlugin

It’s based on some code by Ezra Zygmuntovic extended by me, further extended by Ezra and packaged as a plugin.

It allows for easier creation of the :conditions => … clause in ActiveRecord find statements.

Here’s how to use it:

c = InVisible::Cond.new do
   year '>', 2005
   name 'like', 'Foo%'
Model.find(:all, :conditions => c.where )

or in a combined form:

Model.find_with_conditions(:all) do
   year '>', 2005
   name 'like', 'Foo%'


$cd /my/rails/project
$ruby script/plugin discover
$ruby script/plugin install -x where

The subversion repository is located at https://invisible.ch/svn/projects/plugins/where


You can use the following types of clauses in the definition of the Condition block:

  • name ‘operator’, value
  • name ‘between’, value, value
  • sql ‘some sql statement’, value


  • first_name ‘=’, ‘Ezra’
  • start_date ‘between’, ‘2006-01-01’, ‘2006-01-30’
  • last_name ’like’, ‘Zyg%’
  • sql ‘hosts.id = something.id’

You can extend an existing condition block like this:

c = Cond.new
c < < ['name', 'Jens-Christian']
c << ['age', '>', 30]


There is one caveat, if you use self in the block:

Task.find(:all, :conditions => ["project_id = ?", self.id] )

Task.find_with_conditions(:all) do
    project_id '=', self.id

will break, because self inside the block will refer to another object. A workaround is to use temporary variables:

self_id = self.id
Task.find_with_conditions(:all) do
    project_id '=', self_id

I will see, if there is a better solution for this.

Revision history

v. 0.2 (svn 36), 2.1.2006

  • Added Ezra’s Cond Class
  • removed the Where Class (breaking old code, but the Cond class is nicer)
  • fixed the Model.find_with_conditions method to use the Cond class

Comments, ideas etc. very welcome

Technorati Tags: rubyonrails, sql

Jens-Christian Fischer

Maker. Musician