Multi-part parameter extractor

mkovacs () — Sun, 27 Aug 2006 07:12:24 GMT

For those times when you want to get a date object out of the multi-part parameters without having to do a mass assignment to a model object. I extracted this code directly from AR so I think it should be pretty solid but I have not tested it so your mileage may vary.

Take the following and place it into your application helper or whatever helper you'd like. To use it you simply pass in an instance of the object on which the multi-part parameter exists. This is so that the type to instantiate can be reflected from the column information. Then you specify the attribute name of the parameter you're looking to create from the next parameter which is the hash containing the multi-part parameter value.

example:
for a form containing dude[birth_date] you'd call the method like this:

extract_date(@the_dude, 'birth_date', params[:dude])



    def extract_date(parent_object, param_name, atts)

      atts.stringify_keys!



      multi_parameter_attributes = []

      atts.each do |k, v|

        multi_parameter_attributes << [ k, v ] if k.include?(param_name+"(")

      end

      

      attributes = { }



      for pair in multi_parameter_attributes

        multiparameter_name, value = pair

        attribute_name = multiparameter_name.split("(").first

        attributes[attribute_name] = [] unless attributes.include?(attribute_name)



        unless value.empty?

          attributes[attribute_name] <<

            [ find_parameter_position(multiparameter_name), type_cast_attribute_value(multiparameter_name, value) ]

        end

      end



      attributes.each { |name, values| attributes[name] = values.sort_by{ |v| v.first }.collect { |v| v.last } }

      errors = []

      result = nil

      attributes.each do |name, values|  

        klass = (parent_object.class.reflect_on_aggregation(name.to_sym) || parent_object.column_for_attribute(name)).klass

        result = Time == klass ? klass.local(*values) : klass.new(*values)

      end



      return result

    end

    

    def find_parameter_position(multiparameter_name)

      multiparameter_name.scan(/\(([0-9]*).*\)/).first.first

    end



    def type_cast_attribute_value(multiparameter_name, value)

      multiparameter_name =~ /\([0-9]*([a-z])\)/ ? value.send("to_" + $1) : value

    end

parameterized instance variables

mkovacs () — Tue, 10 Jan 2006 04:24:03 GMT

// useful when you want to obtain more than one instance of the same type of variable on the
// same page. i.e. two different addresses. credit goes to argv[0] in #rubyonrails on freenode



instance_variable_get("@#{address_type}_address").country.name

DZone Snippets: Mkovacs's Code Snippets

Multi-part parameter extractor

parameterized instance variables