Question

This is a beginner’s question but for some reason I cannot find the answer elsewhere.

Customer has_many orders  
Order has_many order_items

I am in customer/show.html.erb and I want my customer to manipulate order_items.

Many orders have many order_items and I want to search ALL of those order_items to find those such that read == false.

#controller
@customer = Customer.find(params[:id])
@orders = @customer.orders

@order_items = @orders.order_items doesn’t work. Given that I have multiple items in @orders, how can I collect all the order_items that belong to @orders?

=== EDIT ===

My entire database structure is a big complicated group of tables and I need to traverse that tree for this particular view.

customer has_many orders
orders has_many order_items
order_items belongs_to category

How do I, for example, find the number of my customer’s order_items that belong to category X?

Last question: why doesn’t @orders.find_all_by_x(…) work?

Answer 1

1) Show all OrderItems for a customer

You can add a relation called “order_items” to your customer like this:

has_many :order_items, :through => :orders

You can then do:

customer = Customer.find(:first)
order_items = customer.order_items

To find all the unread OrderItems (where read == false), you can add a named_scope to your OrderItem:

named_scope :unread, :conditions => {:read => false}

you can then find all unread OrderItems for one customer by:

customer.order_items.unread

2) Show all OrderItems of a Customer belonging to a given Category

Again, a named scope in OrderItem (I assume OrderItem belongs_to Category):

named_scope :in_category, lambda { |name|
  {:conditions => {:categories => {:name => name}}, :include => :category}
}

Two Notes:

1. You have to include :category in the conditon

2. even though its belongs_to :category (singular), you have to use :categories (plural). This is because the :include adds the table as plural. (I don’t know why it does that, and for me this seems like a hint that this is not the best solution.)

Last question: why doesn’t @orders.find_all_by_x(…) work?

This does work as expected for me. What error message are you getting?