Module: Base::ClassMethods

Included in:
ActiveRecord::Base
Defined in:
lib/activerecord/base/class_methods.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#tableless_models ⇒ Object (readonly)

Returns the value of attribute tableless_models.



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# File 'lib/activerecord/base/class_methods.rb', line 4

def tableless_models
  @tableless_models
end

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 => ParentSettings

  # or...

  has_tableless :settings => ParentSettings, :encryption_key => "secret"

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 27

def has_tableless(column)
  encryption_key = column.delete(:encryption_key)
  
  column_name, class_type = column.to_a.flatten

  @tableless_models ||= []
  @tableless_models << column_name
  
  
  # 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; if encryption is enabled, then serialisation/deserialisation will
    # be handled when encrypting/decrypting, rather than automatically by ActiveRecord,
    # otherwise the different object id would cause a different serialisation string each time
    
    serialize column_name unless encryption_key

    # 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
      serialised = read_attribute(column_name) 
      
      value = if encryption_key
        serialised ? YAML::load(ActiveSupport::MessageEncryptor.new(encryption_key).decrypt(serialised)) : serialised
      else
        serialised || {}
      end

      instance   = class_type.new(value)
      
      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|
      v = class_type.new(value)
      v = encryption_key ? ActiveSupport::MessageEncryptor.new(encryption_key).encrypt(YAML::dump(v)) : v
      super v
    end
  end
end