Rails 3.1，has_many：through，habtm

Question

I have the following models:

class Assembly < ActiveRecord::Base
  has_many :manifests
  has_many :parts, :through => :manifests
end

class Manifest < ActiveRecord::Base
  belongs_to :assembly
  belongs_to :part
end

class Part < ActiveRecord::Base
  has_many :manifests
  has_many :assemblies, :through => :manifests
end

Where manifests contains:

assembly_id
part_id
field1
field2
...

How can I update the others fields ( field1 , field2 ...) using habtm?

Answer 1

According to http://guides.rubyonrails.org/association_basics.html#choosing-between-has_many-through-and-has_and_belongs_to_many you have to use a has_many-through instead of a habtm relationship (as you did it in your question). Then, you can simply use this code to set up the relationship between a part and an assembly:

#create assembly
ass1 = Assembly.new
ass1.save!

# create part
part_x = Part.new
part_x.save!

# create relationship between assembly and part using the join model Manifest
Manifest.new(assembly: ass1, part: part_x, field1: 1, field2: "test").save!