Question

I might be doing this wrong overall, but maybe someone will be able to chirp in and help out.

Problem:

I want to be able to build a relationship on an unsaved Object, such that this would work:

v = Video.new
v.title = "New Video"
v.actors.build(:name => "Jonny Depp")
v.save!

To add to this, these will be generated through a custom method, which I’m attempting to modify to work, that does the following:

v = Video.new
v.title = "Interesting cast..."
v.actors_list = "Jonny Depp, Clint Eastwood, Rick Moranis"
v.save

This method looks like this in video.rb

def actors_list=value
  #Clear for existing videos
  self.actors.clear

  value.split(',').each do |actorname|
    if existing = Actor.find_by_name(actorname.strip)
      self.actors << existing
    else
      self.actors.build(:name => actorname.strip)
    end
  end
end

What I expect

v.actors.map(&:name)
=> ["Jonny Depp", "Clint Eastwood", "Rick Moranis"]

Unfortunatey, these tactics neither create an Actor nor the association. Oh yeah, you might ask me for that:

in video.rb

has_many :actor_on_videos
has_many :actors, :through => :actor_on_videos

accepts_nested_attributes_for :actors

I’ve also tried modifying the actors_list= method as such:

def actors_list=value
  #Clear for existing videos
  self.actors.clear

  value.split(',').each do |actorname|
    if existing = Actor.find_by_name(actorname.strip)
      self.actors << existing
    else
      self.actors << Actor.create!(:name => actorname.strip)
    end
  end
end

And it creates the Actor, but I’d rather not create the Actor if the Video fails on saving.

So am I approaching this wrong? Or have I missed something obvious?

Answer 1

Try this:

class Video < ActiveRecord::Base

  has_many :actor_on_videos
  has_many :actors, :through => :actor_on_videos

  attr_accessor :actors_list
  after_save    :save_actors

  def actors_list=names
    (names.presence || "").split(",").uniq.map(&:strip).tap do |new_list|
      @actors_list = new_list if actors_list_changes?(new_list)
    end
  end

  def actors_list_changes?(new_list)
    new_record? or 
      (actors.count(:conditions => {:name => new_list}) != new_list.size)
  end

  # save the actors in after save.
  def save_actors
    return true if actors_list.blank?
    # create the required names
    self.actors = actors_list.map {|name| Actor.find_or_create_by_name(name)}
    true
  end
end