growstuff/app/controllers/likes_controller.rb

class LikesController < ApplicationController
  before_action :authenticate_member!, except: :index

  respond_to :html, :json

  def create
    @like = Like.new
    @like.member = current_member
    @like.likeable = find_likeable

    respond_to do |format|
      if @like.save
        format.html { redirect_to @like.likeable }
        format.json do
          render(
            json: {
              id: @like.likeable.id,
              liked_by_member: true,
              description: ActionController::Base.helpers.pluralize(@like.likeable.likes.count, "like"),
              url: like_path(@like, format: :json)
            },
            status: 201
          )
        end
      else
        format.html do
          flash[:error] = 'Unable to like'
          redirect_to @like.likeable
        end
      end
    end
  end

  def destroy
    like = Like.find(params[:id])
    likeable = like.likeable
    respond_to do |format|
      if like.destroy
        format.html { redirect_to likeable }
        format.json do
          render(
            json: {
              id: likeable.id,
              liked_by_member: false,
              description: ActionController::Base.helpers.pluralize(likeable.likes.count, "like"),
              url: likes_path(Like.new, "#{likeable.class.name.underscore}_id", likeable.id, format: :json)
            },
            status: 200
          )
        end
      else
        format.html do
          flash[:error] = 'Unable to unlike'
          redirect_to likeable
        end
      end
    end
  end

  private

  def find_likeable
    params.each do |name, value|
      return Regexp.last_match[1].classify.constantize.find(value) if name =~ /(.+)_id$/
    end
  end

  def like_params
    params.require(:like).permit(:member, :likeable)
  end
end