Rails Model: How to do the relation - ruby-on-rails

Question

I would like to do an app, but I am stuck on how to design the model. I have these models so far: User, Post, Tag, Like, Comment. I created for each a model, controller, view and migration file. So far so good, BUT now my question is should I just do the relations between them or create these models too: PostTag, PostLike, PostComment. You know, they would just have the relation between those, so when somebody deletes a tag in a post, he actually just deletes the relation and not the tag itself because the tag is maybe used in another post.

Answer 1

You don't need separate models for relations. Just add has_many and belongs_to to existing models and add needed fields (post_id, user_id etc.) to your database tables.
And tags won't disappear when you delete it from a post in case you won't write a code for a tag destroy. Nothing happens by itself.
P.S. I recommend to use acts-as-taggable-on gem for tags

Answer 2

You will only need to add a Tagging model, and use a polymorphic association to handle Likes. So, you need a User, Post, Comment, Like, Tag, and Tagging
You will not need a controller for Tags or Taggings or Likes
If you want users to be able to create posts and comments as well as like both posts and comments, then here is one way to configure your models:
User model:
class User < ActiveRecord::Base
has_many :posts
has_many :comments
has_many :likes, as: :likeable, dependent: :destroy
end
Post model:
class Post < ActiveRecord::Base
belongs_to :user
has_many :comments
has_many :likes, as: :likeable, dependent: :destroy
has_many :taggings
has_many :tags, through: :taggings
def self.tagged_with(name)
Tag.find_by_name!(name).posts
end
def self.tag_counts
Tag.select("tags.*, count(taggings.tag_id) as count").
joins(:taggings).group("taggings.tag_id")
end
def tag_list
tags.map(&:name).join(", ")
end
def tag_list=(names)
self.tags = names.split(",").map do |n|
Tag.where(name: n.strip).first_or_create!
end
end
end
Comment model:
class Comment < ActiveRecord::Base
belongs_to :user
belongs_to :post
end
Like model:
class Like < ActiveRecord::Base
belongs_to :likeable, polymorphic: true
end
Tag migration generator:
rails g model tag name
Tag model:
class Tag < ActiveRecord::Base
has_many :taggings
has_many :posts, through: :taggings
end
Tagging migration generator:
rails g model tagging tag:belongs_to post:belongs_to
Tagging model
class Tagging < ActiveRecord::Base
belongs_to :tag
belongs_to :post
end
The Post model assumes your tag uses the attribute :name
In order to access your tagged Posts add this route
get 'tags/:tag', to: 'posts#index', as: :tag
And change your index action in your Posts controller to this:
def index
if params[:tag]
#posts = Post.tagged_with(params[:tag])
else
#posts = Post.all
end
end
Finally, add a link to your Post Show view like this:
<%= raw #post.tags.map(&:name).map { |t| link_to t, tag_path(t) }.join(', ') %>