How to set karma to appropriate user - ruby-on-rails

Question

I'm trying to add a user karma feature to my app and I'm almost done, just that the karma is being awarded to a different user.
NB, My like system is from scratch and not acts_as_votable.
What I want:
When a user upvotes a book, I want a +1 karma be awarded to the
book.user
If a user's books are downvoted more then they upvoted, I want such
user have negative karma.
What I'm getting:
When a book is upvoted, the user who upvoted the book gets the +1
karma instead of the book.user.
When a user with 0 karma gets his/her book downvoted, the karma incrment by 1 instead of decrementing.
class AddKarmaToUsers < ActiveRecord::Migration[6.0]
def change
add_column :users, :karma, :integer, default: 0
end
end
My code:
vote.rb
class Vote < ApplicationRecord
belongs_to :user
belongs_to :book
validates_uniqueness_of :user_id, scope: :book_id
after_create :increment_vote, :add_karma
after_destroy :decrement_vote, :remove_karma
private
def increment_vote
field = self.upvote ? :upvotes : :downvotes
Book.find(self.book_id).increment(field).save
end
def decrement_vote
field = self.upvote ? :upvotes : :downvotes
Book.find(self.book_id).decrement(field).save
end
def add_karma
user = User.find(self.user_id)
user.increment(:karma, 1).save
end
def remove_karma
user = User.find(self.user_id)
user.decrement(:karma, 1).save
end
end
votes_controller.rb
class VotesController < ApplicationController
def create
book_id = params[:book_id]
vote = Vote.new
vote.book_id = params[:book_id]
vote.upvote = params[:upvote]
vote.user_id = current_user.id
#check if vote by this user exists
existing_vote = Vote.where(user_id: current_user.id, book_id: book_id)
#new_vote = existing_vote.size < 1
respond_to do |format|
format.js {
if existing_vote.size > 0
#destroy existing vote
existing_vote.first.destroy
else
#save new vote
if vote.save
#success = true
else
#success = false
end
# #total_upvotes = #book.upvotes
# #total_downvotes = #book.downvotes
end
#book = Book.find(book_id)
#is_upvote = params[:upvote]
render "votes/create"
}
end
end
private
def vote_params
params.require(:vote).permit(:upvote, :book_id)
end
end

Answer 1

First of all when using active record relations you don't need to call Model.find in the class, just call the relation with it's name:
def increment_vote
field = self.upvote ? :upvotes : :downvotes
book.increment(field).save
end
def add_karma
user.increment(:karma, 1).save
end
In add_karma and remove_karma you are referencing the user that the vote belongs to, and not the user that owns the book. To achieve your goal you should also increment and decrement karma on the book's owner:
def add_karma
user.increment(:karma, 1).save
book.user.increment(:karma, self.upvote ? 1 : -1).save
end
def remove_karma
user.increment(:karma, 1).save
book.user.decrement(:karma, 1).save
end
You could rewrite your controller to simplify the code:
class VotesController < ApplicationController
def create
#vote = current_user.votes.find_or_initialize_by vote_params[:book_id]
#vote.assign_attributes vote_params
#success = #vote.save
# instead of #book = #vote.book just use #vote.book in your view
#book = #vote.book
# instead of #is_upvote you can use #vote.upvote in your view
#is_upvote = #vote.upvote
respond_to do |format|
format.js { render 'votes/create'}
end
end
private
def vote_params
params.require(:vote).permit(:upvote, :book_id)
end
end