Module: TranslateColumns::ClassMethods

Defined in:
lib/translate_columns.rb

Overview

methods used in the class definition

Instance Method Summary collapse

Instance Method Details

#translate_columns(*options) ⇒ Object

Read the provided list of symbols as column names and generate methods for each to access translated versions.

Possible options, after the columns, include:

  • :locale_field - Name of the field in the parents translation table

of the locale. This defaults to ‘locale’.



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# File 'lib/translate_columns.rb', line 27

def translate_columns( *options )
   
  locale_field = 'locale'
  
  columns = [ ]
  if ! options.is_a? Array
    raise "Provided parameter to translate_columns is not an array!"
  end
  # extract all the options
  options.each do | opt |
    if opt.is_a? Symbol
      columns << opt
    elsif opt.is_a? Hash
      # Override the locale class if set.
      locale_field = opt[:locale_field]
    end
  end

  define_method 'columns_to_translate' do
    columns.collect{ |c| c.to_s }
  end
  
  # set the instance Methods first
  include TranslateColumns::InstanceMethods
  
  # Rails magic to override the normal save process
  alias_method_chain :save, :translation
  alias_method_chain :save!, :translation
  alias_method_chain :attributes=, :locale

  # Generate a module containing methods that override access 
  # to the ActiveRecord methods.
  # This dynamic module is then included in the parent such that
  # the super method will function correctly.
  mod = Module.new do | m |
    
    columns.each do | column |

      next if ['id', locale_field].include?(column.to_s)
    
      # This is strange, so allow me to explain:
      #  We define access to the original method and its super,
      #  a normal "alias" can't find the super which is the method
      #  created by ActionBase.
      #  The Alias_method function takes a copy, and retains the 
      #  ability to call the parent with the same name.
      #  Finally, the method is overwritten to support translation.
      #  
      #  All this is to avoid defining parameters for the overwritten
      #  accessor which normally doesn't have them.
      #  (Warnings are produced on execution when a metaprogrammed
      #  function is called without parameters and its expecting them)
      #  
      #  Sam Lown (2007-01-17) dev at samlown dot com
      define_method(column) do
        # This super should call the missing_method method in ActiveRecord.
        super()
      end
      
      alias_method("#{column}_before_translation", column)
      
      # overwrite accessor to read
      define_method("#{column}") do
        if translation and ! translation.send(column).blank?
          translation.send(column)
        else
          super()
        end
      end
      
      define_method("#{column}_before_type_cast") do 
        if (translation)
          translation.send("#{column}_before_type_cast")
        else
          super()
        end
      end
      
      define_method("#{column}=") do |value|
        # translation object must have already been set up for this to work!
        if (translation)
          translation.send("#{column}=",value)
        else
          super( value )
        end  
      end          

    end
  end # dynamic module

  # include the anonymous module so that the "super" method
  # will work correctly in the child!
  include mod
end