Rails 4 cache_counter for has_and_belongs_to_many relationship

console.rb

## I imagine this could be done in the migration, but it was giving me problems so I moved it to the model 
## and just did it on the command line
 
> Tag.reset_questions_count

migration-sometimestamp.rb

class AddQuestionsCounterToTags < ActiveRecord::Migration
  def up
    add_column :tags, :questions_count, :integer, default: 0, null: false
  end
  
  def down
    remove_column :tags, :questions_count
  end
    
end

question.rb

class Question < ActiveRecord::Base
  ## the validates_tag method is just to prevent duplicate tags being added to the db - not fully necessary for this exercise, 
  ## but I figured I would leave it just in case
  has_and_belongs_to_many :tags, before_add: :validates_tag
  
  after_create :increment_tags_counter
  before_destroy :decrement_tags_counter
  
  protected
  
  def validates_tag(tag)
    self.tags.include? tag
  end
 
  def increment_tags_counter
    self.tags.each {|t| t.increment!(:questions_count) }
  end

  def decrement_tags_counter
    self.tags.each {|t| t.decrement!(:questions_count) }
  end
 
end

tag.rb

class Tag < ActiveRecord::Base
  has_and_belongs_to_many :questions, -> { uniq }
 
  def self.reset_questions_count
    Tag.find_each do |t|
      t.update(questions_count: t.questions.count)
    end
  end  
 
end