I'm not satisfied with how rails currently handles finds accross active record models, and want to see if there's a waywe can improve it.
The ability to generate dynamic search criteria from forms that search accross models can be quite difficult except in the simplest cases. The main cause of this is because as a developer you have to work out what the table name is going to be called before you are able to use it.
Here is an example:
class Person < ActiveRecord::Base
# Everybody has a home address belongs_to :home_address, :class_name => 'Address', :foreign_key => 'home_address_id'
# Only some people have a work address belongs_to :work_address, :class_name => 'Address', :foreign_key => 'work_address_id' end
class Address < ActiveRecord::Base end
Lets say we have a search panel, that allows you to filter on home address street name, and work address street name and the user may or may not use these search options.
# A search for the home address 22 Person.find(:all, :joins => [:home_address, :work_address], :conditions => {:address => {:street_no => 22}})
# A search for the work address 22 Person.find(:all, :joins => [:work_address, :home_address], :conditions => {:address => {:street_no => 22}}) #Notice that the order of the joins affects what the conditions hash applies too. I believe this unintuitive.
# I think a better system would be to use the names of the relationships to dictate the search criteria # This would stop the user having to guess what the join table is called.
Person.find(:all, :joins => [:work_address, :home_address], :conditions => {:home_address => {:street_no => 22}})
# If this could be developed I would think we'd need to cover these cases: # 1. Eager loading using inner join Person.find(:all, :joins => [:work_address, :home_address], :conditions => {:home_address => {:street_no => 22}})
# 2. Eager loading using left join # Notice that the home_address has conditions specified so in this case we might want to enforce a left join Person.find(:all, :include => [:work_address, :home_address], :conditions => {:home_address => {:street_no => 22}})
# 3.No eager loading specified (would we force a join because of the conditions specified?) Person.find(:all, :conditions => {:home_address => {:street_no => 22}})
# 4. Custom SQL for each nesting, so that you can use any sql but not have to explicitly know the name of the table Person.find( :all, :joins => :home_address :conditions => [ {:age => 22}, # This would currently conflict with the currect nested hash since {:home_address => ['home_address.street_name LIKE ?', 'Dougla%']} ] )
# 1. Joins # SELECT * # FROM people # JOIN addresses home_address ON (people.home_address_id = home_address.id) # WHERE people.age = 22 AND # home_address.street_name LIKE 'Dougla%'
# 2. Left Joins (:include) # SELECT * # FROM people # WHERE people.age = 22