在导轨HABTM与HM / BT中模拟“喜欢”

Question

What would be the best method to model "likes" in rails for my app. I could either to the following:

class User < ActiveRecord::Base
  has_many :things

  has_many :likes
  has_many :liked_things, through: :likes, source: :thing
end

class Like < ActiveRecord::Base
  belongs_to :user
  belongs_to :thing
end

class Thing < ActiveRecord::Base
  belongs_to :user

  has_many :likes
  has_many :liking_users, through: :likes, source: :user
end

Or

class User < ActiveRecord::Base
  has_many :things

  has_and_belongs_to_many :things
end

class Thing < ActiveRecord::Base
  belongs_to :user

  has_and_belongs_to_many :users
end

What approach would be best and why? I plan to have an activity feed in my app as well, if that helps determine the best approach.

Answer 1

The answer to this question depends on whether or not Like will ever have any attributes or methods.

If its only purpose of existence is to be the HABTM relationship between User s and Thing s, then using the has_and_belongs_to_many relationship would suffice. In your example, having has_many and belongs_to is redundant. All you would need in this case is:

class User < ActiveRecord::Base
  has_and_belongs_to_many :things
end

class Thing < ActiveRecord::Base
  has_and_belongs_to_many :users
end

On the other hand, if you anticipate that a Like will have an attribute (eg maybe someone will really like something, or love it, etc.) then you can do

class User < ActiveRecord::Base
  has_many :likes
  has_many :liked_things, through: :likes, source: :thing
end

class Like < ActiveRecord::Base
  belongs_to :user
  belongs_to :thing
end

class Thing < ActiveRecord::Base
  has_many :likes
  has_many :liking_users, through: :likes, source: :user
end

Note that I removed has_many :things and belongs_to :user as they are redundant.