I'm not sure if rails can manage this for you, but in the past when I have two objects that access the same object I've created a tying table (not sure if this is the right way to say it). For example, an organization and an individual both can have many addresses. While I could create an org_addresses and an ind_addresses table I'd rather not manage two tables of addresses when I could just create two tying tables. My tables would look like this: Organizations id Org_Addresses (tying table) organiation_id addresses_id Address id ------------ Individuals id Ind_Addresses (tying table) individual_id addresses_id Address id This would allow me to manage addresses in one place but still be able to access the individuals and the organizations addresses by using the tying table. How would one go about doing this in rails? I've done this many times, but am new to rails.
on 2007-05-16 17:32
on 2007-05-16 17:47
Hey, The table you call a 'tying' table is also called a 'join' table. It is part of what it is known as a 'has and belongs to many' relationship. The good news is that Rails handles this very easily. Let's take the Organizations - Addresses relationship. First you'll create your models and tables. You'll end up with these tables: organizations addresses Then you need to create the join table: addresses_organizations ------------------------------------ address_id organization_id ------------------------------------ Rails assumes that your join table is named after the 2 related classes, in plural and alphabetical order. Next you tie this up in you models: class Organizations < ActiveRecord::Base has_and_belongs_to_many :addresses end class Addresses < ActiveRecord::Base has_and_belongs_to_many :organizations end That's it for the tieing up. You can then do things like this: organization = Organization.find_by_name('Company name') organization.addresses << Address.find_by_postcode('TE5 TID') And Rails will do the rest. Just repeat that for your Individual class and you should be good to go. Steve
on 2007-05-16 18:33
Great! thanks steve, one question though...if I then want to force an address to be associated with an organization do I need to manage this or does rails do that for me? If so, how? For example, if I want to add a address to an existing organziation does rails manage that for me or do I need to specifically code that association?
on 2007-05-16 19:17
Well you kinda need to write the code to add the address. It'd look something like this: Let's say you've got an 'add address' form and it posts to an action that you want to add the address to an existing organization: # Create and validate the new address address = Address.new(params[:address]) if address.save # Find the existing organization organization = Organization.find_by_id(params[:organization_id]) # Associate the address with this organization organization.addresses << address end Obviously there's a lot more to getting it to work than that code, but I hope it demonstrates the concept. Steve -- www.stephenbartholomew.co.uk www.curve21.com
on 2007-05-17 15:41
Thanks... It's all coming together real nicely. I'm probably over using the join table concept now. :)