Structuring Active Record relationships

rubyonrails-talk
1

Hi,

I have three tables: Expenses, Vendors and Vendor _Accounts

It should operate as follows: When a new Expense record is created, A vendor is selected from a drop-down of Vendors and, An account is selected from a drop-down of Vendor_Accounts where Vendor_Accounts#vender == selected vendor

So I should have a structure something like: class Expense   has_one Vendor

class Vendor   has_many Vendor_Accounts where Vendor#id == Vendor_Accounts#vendor   belongs_to Expense

class Vendor_Account   belongs_to Vendor

I don’t think I should have Expense, Vendor and Account tables because the accounts defined by each vendor bear no relationship with the other vendors’ account beyond the mere concept of “account”.

Does this make sense, and if so, how precisely should I describe these relationships? Am I close with the above idea?

BTW, I'm running Rails 2.3.5, Ruby 1.8.6, WinXP-Pro/SP3, Firefox 3.6.2, Firebug 1.5.3, MySQL 5.0.37-community-nt, Mongrel, Apache HTTP Server 2.2.15

Thanks in Advance, Richard

2

Thinking about it some more, I now think I should have separate Expense, Vendor and Account tables with the following relationships:

class Expense   has_one Vendor

class Vendor   has_many Accounts   belongs_to Expense

class Account   belongs_to Vendor

Then an Expense record can get Accounts through Vendor. .. or something like that.

Am I getting warmer?

Thanks in Advance, Richard

3

Expense would belong to Vendor, not have one Vendor, unless you are planning to put the foreign key in the vendors table, which sounds very strange, as that would require a new vendor to be created for every expense. If you are fist selecting a vendor, and then selecting an account belonging to that vendor when you create an expense, then it makes sense to hook expense up to account, not vendor.

class Vendor   has_many :accounts

class Account   belongs_to :vendor   has_many :expenses

class Expense   belongs_to :account

Then when you have created an expense you can get its account through @expense.account and its vendor through @expense.account.vendor. Does this make sense?

4

Hi Sharagoz,

Does this make sense?

Absolutely! It's crystal clear.

Many thanks, Richard