Question

I am trying to build a twitter like data model in rails. This is what I have come up with.

class User < ActiveRecord::Base
  has_many :microposts, :dependent => :destroy
end

class Micropost < ActiveRecord::Base
  belongs_to :user
  has_many :mentions
  has_many :hashtags
end

class Mention< ActiveRecord::Base
  belongs_to :micropost
end

class Hashtag < ActiveRecord::Base
  belongs_to :micropost
end

Should I be using a has_many through association somewhere or is this accurate?

Edit: The final twitter MVC model.

class User < ActiveRecord::Base
  has_many :microposts, :dependent => :destroy

  userID
end

class Micropost < ActiveRecord::Base
  belongs_to :user

  has_many :link2mentions, :dependent => :destroy
  has_many :mentions, through: :link2mentions

  has_many :link2hashtags, :dependent => :destroy
  has_many :hashtags, through: :link2hashtags

  UserID
  micropostID
  content
end

class Link2mention < ActiveRecord::Base
    belongs_to :micropost
    belongs_to :mention

    linkID
    micropostID
    mentionID
end

class Mention < ActiveRecord::Base
  has_many :link2mentions, :dependent => :destroy
  has_many :microposts, through: :link2mentions

  mentionID
  userID
end

Edit 2: A concise and accurate explanation

http://railscasts.com/episodes/382-tagging?view=asciicast

Answer 1

If two microposts use the same hashtag, you probably don’t want to create two database records for that hashtag. In this case you would use has_many through:

class Hashtagging < ActiveRecord::Base
  belongs_to :micropost
  belongs_to :hashtag
end

class Hashtag < ActiveRecord::Base
  has_many :hashtaggings
  has_many :microposts, through: :hashtaggings
end

class Micropost < ActiveRecord::Base
  ...
  has_many :hashtaggings
  has_many :hashtags, through: :hashtaggings
end

When you create the Hashtagging migration, make sure it has the micropost_id and hashtag_id columns.