Validate the number of has_many items in Ruby on Rails

Question

Users can add tags to a snippet:

class Snippet < ActiveRecord::Base

  # Relationships
  has_many :taggings
  has_many :tags, :through => :taggings
  belongs_to :closing_reason

end

I want to validate the number of tags: at least 1, at most 6. How am I about to do this? Thanks.

Answer 1

You can always create a custom validation.

Something like

  validate :validate_tags

  def validate_tags
    errors.add(:tags, "too much") if tags.size > 5
  end