Little add in module to make parameter parsing a little easier in Virtus classes.

command.rb

class Command
  include ActiveModel::Validations
  include ActiveRecord::Serialization
  include Virtus
  include VirtusParameters
 
  def initialize(params = {})
    super
    parse_params params
  end
  
  # All your command execution stuff goes here...
end

virtus_parameters.rb

# You must include this module after including Virtus in your class
module VirtusParameters
  ID_PARAMETER = /(\w+)_id$/
 
  extend ActiveSupport::Concern
 
  def parse_params(params)
    params.reject{|_,v| v.nil?}.each {|name, value| parse_param(name, value)}
  end
 
  def parse_param(name, value)
    if (match = ID_PARAMETER.match(name.to_s)) &&  (ar_class = self.class.active_record_types[match[1].to_sym])
      value = ar_class.find(value)
      name = match[1].to_sym
    end
    send("#{name}=", value) if attributes.keys.include?(name)
  end
 
  module ClassMethods
    def attribute(name, type = Object, options = {})
      active_record_types[name] = type if (type.is_a?(Class) && type < ActiveRecord::Base)
      super
    end
 
    def active_record_types
      @active_record_types ||= {}
    end
 
  end
end

This is a simple add in to make the parsing of parameters in Virtus objects a bit less repetitive. We build command objects based upon Virtus and they often reference ActiveRecord objects.

This add in accomplishes two things when constructing from a hash:

• If a key in the hash corresponds to an attribute in the class, it is assigned directly
• If a key in the hash corresponds to an attribute in the class with a _id extension, and that attribute is an ActiveRecord::Base, then the module will find the model for that id.