Question

What is analog in datamapper for .present? method?

I have code from rails app an d wan t to reuse it is Sinatra

ex:

  def encrypt_password
    if password.present?
      self.password_salt = BCrypt::Engine.generate_salt
      self.password_hash = BCrypt::Engine.hash_secret(password, password_salt)
    end
  end

in model I ave before save callback

before :save, :encrypt_password

Answer 1

The present? Method in ActiveSupport is defined as follows:

class Object
    def present?
      !blank?
    end

    def blank?
      respond_to?(:empty?) ? empty? : !self
    end
end

(Source: http://api.rubyonrails.org/classes/Object.html#method-i-present-3F)

You could extend Object like that, too. It checks whether the Object is not blank. The method blank? itself checks whether the Object responds to empty?. This is mostly for strings. If the Object does not respond to empty?, the method simply returns !self. So present? would simply return self. Therefore you could also write your code as

  def encrypt_password
    if password
      self.password_salt = BCrypt::Engine.generate_salt
      self.password_hash = BCrypt::Engine.hash_secret(password, password_salt)
    end
  end

The only advantage of the present? method is, that it does not treat an empty string as present, whereas the second method does.