help with model relationship for Product/Bill of Materials

rubyonrails-talk
1

I am struggling to find the best way to set up relationships to achieve this so that it fits the rails idioms.

I have a table of products and I want to be able to create a bill of materials for a product..

So a product can either be a single item, or a package consisting of several other products.

I have created a table:

2

Tony, I'm currently working on the same thing but have decided to make BOM's a separate entity and not an item in the item file. Thus I have an Assembly table that has many Assyitems. These Assytitems hold foreign keys to the Item table. This works well when users don't have to do nested BOM's. Kathleen

3

Kathleen,

thanks for the suggestion. I thought about pulling BOM out to a separate model that would be used to reference the BOM Items. I went backwards and forwards a few times and decided to try it with just the bom_items and see if I was losing any functionality. Still putting together the view to allow BOMs to be created for a product, I will see how it works out.

Thanks Tony

4

Keeping your BomItem model pretty much as is you could have

class Product ...   has_many :bom_items   has_many :components, :through => :bom_items end

This gives you what you've already got.

Then you can say

has_many :bom_uses, :foreign_key => 'component_id', :class_name => 'BomItem' has_many :uses, :through => :bom_uses, :source => :product

(please think of better names than I have :slight_smile: Then given a production, p.components are the products it is made of, and p.uses is the products that uses it as a component

Fred