Rails: Methods gained via Associations

AssociationMethods

//***** ------- Order belongs_to Customer ==> methods gained:
@order.customer
@order.customer=
@order.build_customer(customer_number: 123, customer_name: "Joe Blow") --> only creates customer instance ... does not save!
@order.create_customer((customer_number: 123, customer_name: "Joe Blow") --> creates instance and saves it!
@order.create_customer!( ... ) --> raises error if record is not valid


//***** ------- Customer has_many Orders ==> methods gained:
@orders = @customer.orders
@customer.orders << (@order1, @order2, ...)  --> //adds orders to collection
@customer.orders.delete(@order1, @order2, ...) --> deletes from collection by setting foreign key to NULL
@customer.orders.destroy(@order1, @order2, ...) --> deletes by calling destroy on each object
@customer.orders=objects --> forces collection to only contain "objects"
@customer.order_ids --> returns array of 'ids' in the collection
@customer.order_ids=ids --> forces collection to contain only orders with the given ids
@customer.orders.clear  --> removes all orders from the collection
@customer.orders.empty? --> checks to see if 'orders' collection is empty
@customer.orders.size  --> returns the # of orders in the collection
@customer.orders.find(...) --> finds objects within the collection 
@customer.orders.where(...) --> finds objects in collection based on conditions given
@customer.orders.exists?(...) --> checks if object exists in collection based on conds. given
@customer.orders.build(attributes = {}, ...) --> returns one or more methods based attrs
@customer.orders.create(attributes = {}) --> returns & saves object(s) based on attrs
@customer.orders.create!(attributes = {}) --> raises "invalid" if record is invalid


//***** ------- Part has_and_belongs_to_many Assemblies ==> methods gained:
// The xxact same methods as the has_many association, but it goes both ways for the objects in question
@part.assemblies ... etc
@assembly.parts ... etc