saving to join model has_many :through

Question

Sequences are acting as a join table between procedures and steps:

  create_table "procedures", :force => true do |t|
    t.integer  "procedure_id"
    t.integer  "revision"
    t.string   "description"
  end

  create_table "sequences", :force => true do |t|
    t.integer  "procedure_id"
    t.integer  "step_id"
    t.integer  "step_number"
  end

  create_table "steps", :force => true do |t|
    t.string   "descriptor"
    t.string   "step_category"
    t.string   "step_type"
    t.text     "instructions"
  end

What I am trying to do is to create a procedure, then create a step from the procedure, and have it save the step_number in the sequence associating the step and the procedure at the same time.

1. Is there any good guide on how to do has_many :through? All I ever find is just how to make the model, I have no idea how to work with it.
2. When saving my Step, do I need to explicitly create a Sequence? I was hoping Rails would automagically create it.

If anyone has some pointers on how to do this I would be glad to hear them, I'm having a lot of trouble setting this up.

Answer 1

Rails does not automatically create join records for you expect when using "has and belongs to many". If you are using "has many :through" you will have to explicitly create the join record. However, this doesn't stop you from making a helper method to do some of the dirty work for you.