How to get information from a join table when looping over has_many :through

Question

I have a has_many :through association, and I am iterating over the children to put together some info. But I would also like to get some information out of the join table in the loop. Here is the method with blaring comments around the section that needs help. Am I able to get that membership number from the join table in a simple manner like this?

class Customer < ActiveRecord::Base
has_many :customer_memberships
has_many :membership_programs, :through => :customer_memberships

def membership_info_to_json
  info ={"benefits" => [], "omitted_stuff" => {}}
  self.membership_programs.each do |membership|
    ##################################################################
    #THIS INFO IS IN THE JOIN TABLE ##################################
    info["membership_numbers"] << customer_membership.membership_number 
    ##################################################################

    #Omitted: the rest of the loop deals with membership.
  end
  info.to_json
end

Answer 1

Something about your attempt is confusing me. I'm not exactly sure what it is but unless I'm mistaken, a membership_program is going to also have many customer_memberships. If that's the case then you'll have to collect each for that membership.

def membership_info_to_json
  info ={"membership_numbers"=>[], "benefits" => [], "omitted_stuff" => {}}
  self.membership_programs.each do |membership|
    info["membership_numbers"] << membership.customer_memberships.collect{|cm| cm.membership_number} 
  end
  info["membership_numbers"].flatten!
  info.to_json
end 

I hope that helps.