    require 'quickfix_ruby'

    class MyStringField < Quickfix::StringField
    	def initialize( data = nil )
    		if( data == nil )
    			super(6123)
    		else
    			super(6123, data)
    		end
    	end
    end

    class MyDoubleField < Quickfix::DoubleField
    	def initialize( data = nil )
    		if( data == nil )
    			super(8756)
    		else
    			super(8756, data)
    		end
    	end
    end