Module: Base::ClassMethods

Defined in:
lib/activerecord/base/class_methods.rb

Instance Method Summary collapse

Instance Method Details

#has_tableless(column) ⇒ Object

Macro to attach a tableless model to a parent, table-based model. The parent model is expected to own a property/column having as name the first argument (or the key if the argument is a hash )

Can be used this way:

class Parent < ActiveRecord::Base

  has_tableless :settings

  # or...

  has_tableless :settings => ParentSettings

end

NOTE: the serialized column is expected to be of type string or text in the database



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# File 'lib/activerecord/base/class_methods.rb', line 25

def has_tableless(column)
  column_name = column.class == Hash ? column.collect{|k,v| k}.first.to_sym : column
  
  # if only the column name is given, the tableless model's class is expected to have that name, classified, as class name
  class_type = column.class == Hash ? column.collect{|k,v| v}.last : column.to_s.classify.constantize


  # injecting in the parent object a getter and a setter for the
  # attribute that will store an instance of a tableless model
  class_eval do

    # Telling AR that the column has to store an instance of the given tableless model in 
    # YAML serialized format
    serialize column_name, ActiveRecord::TablelessModel

    # Adding getter for the serialized column,
    # making sure it always returns an instance of the specified tableless
    # model and not just a normal hash or the value of the attribute in the database,
    # which is plain text
    define_method column_name.to_s do
      instance = class_type.new(read_attribute(column_name.to_sym) || {})
      
      instance.__owner_object         = self
      instance.__serialized_attribute = column_name
      
      instance
    end

    # Adding setter for the serialized column,
    # making sure it always stores in it an instance of 
    # the specified tableless model (as the argument may also be a regular hash)
    define_method "#{column_name.to_s}=" do |value|
      super class_type.new(value)
    end
  end
end