How to convert a method into a scope.

Question

Hello I am trying to convert the method self.liked_by(user) into a scope. I am not entirely sure what my instructor is asking for so any interpretations on the question are greatly appreciated.

this is the method in question that I am supposed to turn into a scope.

def self.liked_by(user)
    joins(:likes).where(likes: { user_id: user.id })
end

this is where the method appears in the model

class Bookmark < ActiveRecord::Base
  belongs_to :user
  belongs_to :topic
  has_many :likes, dependent: :destroy
  before_validation :httpset
  validates :url, format: { with: /\Ahttp:\/\/.*(com|org|net|gov)/i,
    message: "only allows valid URLs." }

  def self.liked_by(user)
    joins(:likes).where(likes: { user_id: user.id })
  end

  def  httpset
    if self.url =~ /\Ahttp:\/\/|\Ahttps:\/\//i
    else
      if self.url.present?
        self.url = "http://"+ self.url
      else
        self.url = nil
      end
    end
  end
end

And this is where the method is called in the controller

class UsersController < ApplicationController
  def show
    user = User.find(params[:id])
    @bookmarks = user.bookmarks
    @liked_bookmarks = Bookmark.liked_by(user)
  end
end

Thanks for looking at my problem and have a good day.

Answer 1

@liked_bookmarks = Bookmark.liked_by(user)

In this line, in the same way you send the user parameter to a method, the same way you can send it to a scope.

class Bookmark < ActiveRecord::Base
   ---------
   ---------
   scope :liked_by, ->(user) { joins(:likes).where(likes: { user_id: user.id }) }
   ---------
   ---------
  end 

the parameter you sent from the scope call can be accessed using the (user{or any name) in the scope

reference of scopes

Answer 2

As Owen suggested, read the docs to understand what scopes are. It is just another syntax to define your model's class methods (just like the one you already have).

scope :liked_by, ->(user) { joins(:likes).where(likes: { user_id: user.id }) }