CODEWITHSUNDEEP
ruby-on-railsruby
MorphicPro
MorphicPro

Reputation: 2902

Proper Association Design

I have a need to do one query on a record set and get list of many type objects.

In this example I will use a blog post which a blog post has many different types.

Base Post:

class Post < ActiveRecord::Base
  belongs_to :postable, :polymorphic => true
  attr_accessible :body, :title
end

Audio Post:

class AudioPost < ActiveRecord::Base
  attr_accessible :sound
  has_one :postable, :as => :postable
end

Graphic Post:

class GraphicPost < ActiveRecord::Base
  attr_accessible :image
  has_one :postable, :as => :postable
end

This will allow me to do something like this. 

@post = Post.all
@post.each do |post|
  post.title
  post.body
  post.postable.image if post.postable_type == "GraphicPost"
  post.postable.sound if post.postable_type == "AudioPost" 
end

Though this works, it feels wrong to check the type because that goes against the duck type principle. I would assume there is a better way then this to do the same thing.

What is be a better design to achieve this same goal or am I just over thinking my design?

Upvotes: 0

Views: 88

Answers (1)

sites
sites

Reputation: 21785

See my comments.

Anyway, if you want polymorphic, I would write logic in model:

class Post
  delegate :content, to: :postable


class AudioPost
  alias_method :sound, :content


class GraphicPost
  alias_method :image, :content

You will want to render images different than a sound, for that part, I would use a helper:

module MediaHelper
  def medium(data)
    case # make your case detecting data type
    # you could print data.class to see if you can discriminate with that.

and call in view

= medium post.content

Upvotes: 2

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