Question

I have the following setup:

class Program
   has_many :participants
end

class Participant
   belongs_to :user
end

class User
   has_many :participants
end

I want class method or scope to return all the programs in which a certain user participates. Here’s what I have so far:

def self.where_user_participates(user)
   Program.joins(:participants).where('participants.user_id' => user.id)
end

I believe that works but I am not in love with it. I prefer not to talk about ‘id’s but use the associations, but I could not get it to work, e.g.:

def self.where_user_participates(user)
  Program.joins(:participants).where('participants.user' => user)
end

How can I improve this? And is it true that official ‘scope’s are not needed and a class method is ‘best practice’ in Rails 3?

Answer 1

class Program
  has_many :participants
end

class Participant
  belongs_to :user
  belongs_to :program
end

class User
  has_many :participants
  has_many :programs, :through => :participants
end

Then to get the programs call:

user.programs