About rails polymorphic - ruby-on-rails

Question

I have three models , Article, User, Approval. and this is the Approval table
def change
create_table :approvals do |t|
t.references :user, foreign_key: true
t.references :approvable, polymorphic: true
t.timestamps
end
end
this is the three models
class User < ApplicationRecord
has_many :approvals
has_many :articles, dependent: :destroy
end
class Article < ApplicationRecord
belongs_to :user
has_many :approvals, as: :approvable
end
class Approval < ApplicationRecord
belongs_to :user
belongs_to :approvable, polymorphic: true
end
now i want to show an approval image in the article show page, and it's diffenrence according if the current_user has approved the article, i think there is a very eazy way to do this, but i can only come up with a stupid way to
do this, like :
<% #article.approvals.each do |approval| %>
<% if approval.user_id == current_user.id %>
# show has approvaled image
<% end %>
<% end %>
i think it maybe inefficient, please tell me a better solution, Thanks! : )
maybe i didn't express very well, i mean the approval is praise or like?

Answer 1

You can first check for approvals which belongs to current_user and article.
So in controller method use(considering you have only one article at a time),
#current_user_approvals = Approval.where(user_id: current_user.id, article_id: #article.id)
and then use #current_user_approvals in view as,
<% #current_user_approvals.each do |approval| %>
# show has approval image
<% end %>

Answer 2

Polymorphic should not be used in this case. you can use has_many :through to achieve approval. read the docs here
the migration would be:
class CreateApprovals < ActiveRecord::Migration[5.0]
def change
create_table :approvals do |t|
t.belongs_to :user
t.belongs_to :article
end
end
end
models would be like:
class User < ApplicationRecord
has_many :articles, dependent: :destroy
has_many :approvals
has_many :approved_articles, through: :approvals, source: :article
end
class Article < ApplicationRecord
belongs_to :user
has_many :approvals
has_many :approved_users, through: :approvals, source: :user
end
class Approval < ApplicationRecord
belongs_to :user
belongs_to :article
end
Now we can do the tricks (in rails console):
# create a user
user = User.create(name: 'user')
# create an article
article = user.articles.create(name: 'article')
# check whether article is approved
user.approved_articles.include?(article) # => false
# approve the article
user.approved_articles << article
# check check whether article is approved again
user.approved_articles.include?(article) # => true
edited version, since we do want to use polymorphic on approvals. the key is to use source_type to specify the polymorphic type (in this case it's 'Article')
class User < ApplicationRecord
has_many :articles, dependent: :destroy
has_many :approvals
has_many :approved_articles, through: :approvals, source: :approvable, source_type: 'Article'
end
class Article < ApplicationRecord
belongs_to :user
has_many :approvals, as: :approvable
has_many :approved_users, through: :approvals, source: :user
end
class Approval < ApplicationRecord
belongs_to :user
belongs_to :approvable, polymorphic: true
end
tests above in console still work.