如何在 rails 中包含当前用户是否喜欢某个帖子？

Question

So I have a query with gets all the recent posts

posts = Post.where(public: true).limit(25).order(created_at: :desc)

which returns the posts that I need. now I want to return the post but I also want to include if the user who is making the call has liked the post.

I have a like table that just has the post_id, and user_id.

right now the way I have it is

render :json => posts.as_json(:include => [:likes])

which returns all the people who have liked the post which is not what I want:

{
    "id": 43,
    "title": "asdfasdfs",
    "story": "adfaf sdf sd asdf sdf asdf saf adf",
    "created_at": "2017-05-10T22:40:54.587Z",
    "updated_at": "2017-05-10T23:18:47.653Z",
    "user_id": 8,
    "likes": [
      {
        "id": 1,
        "user_id": 4,
        "post_id": 43
      },
      {
        "id": 2,
        "user_id": 6,
        "post_id": 43
      }
    ]
  }

I either want to just include the like that is by the user (somehow having a wherein the include to limit it)

or to somehow just make it a variable in the JSON called liked_by_me set to true or false. I am trying to avoid though having to do a map by hand and doing another 25 more queries, one for each post to see if it was liked by someone. What's the best way to do this?

Thanks

Answer 1

You should query the many-to-many table with the current user's id and the post id, and if that record exists, this means that the user liked that post. Store the like similar to how you stored the posts, but adding where clauses for the user id and the post id. If the row exists, it returns the row, if not, it will return nil.

Answer 2

I had similar 'problem' (instead of posts I had articles but it doesn't matter). The way I choose to deal with this is as follows:

User model looks like this:

class User < ActiveRecord::Base
  has_many :articles ,dependent: :destroy 
  has_secure_password
  has_many :likes 
end

Article model:

class Article < ActiveRecord::Base
    belongs_to :user
    has_many :likes
end

and the Like model :

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

Likes controller should looks like :

def create
  @like=Like.new(article_id:params[:article_id],user_id:params[:user_id])

  if !(Like.find_by(user_id: params[:user_id], article_id: params[:article_id]))
     if current_user!=Article.find(params[:article_id]).user
       if @like.save
         flash[:success]='Thanks for your like'
         redirect_to article_path(params[:article_id])
       else
         render 'new'
       end
     else
       flash[:warning]="You can't like your article"
       redirect_to article_path(params[:article_id])
     end
  else
     flash[:danger]='You liked this article once'
     redirect_to article_path(params[:article_id])      
  end
end

Code for current_user :

  def current_user
    @current_user ||=User.find(session[:user_id]) if session[:user_id]
  end

In articles show template I've rendered the partial template named '_likes'

<%= render 'likes' %>

and I think what you are asking about is shown in these lines from partial template '_likes'

  <% if !Like.find_by(user_id: current_user, article_id:@article.id) %>
    <img src="/assets/no_like.png">
  <% else %>
    <img src="/assets/like.png">
  <% end %>

If you are logged in and you haven't yet liked an article the show template would look like : Article with no like from the user logged in

Another case : If you are logged in and you've liked the article the show template would looke like : Article with like from you

I hope this will help you.

Answer 3

class User < ActiveRecord::Base
  has_many :articles ,dependent: :destroy 
  has_secure_password
  has_many :likes 
end

class Article < ActiveRecord::Base
    belongs_to :user
    has_many :likes

    def liked?(user)
      !!self.likes.find{|like| like.user_id==user.id}
    end

end

class Like < ActiveRecord::Base
  validates :user_id, uniqueness: { scope: [:article_id]}
  belongs_to :article
  belongs_to :user
end

Then you check:

if @article.liked?(@current_user)

Reference: https://medium.com/swlh/how-to-add-a-simple-like-button-to-your-rails-6-application-c1040999dc2