TypeCaster module

type_caster.rb

class Boolean
  def self.from_json(value)
    if value.is_a?(TrueClass) || value.is_a?(FalseClass)
      return value
    elsif value.is_a?(String)
      return value == ("true" || "1")
    elsif value.is_a?(Integer)
      return value == 1
    else
      nil
    end
  end
end
def String.from_json(value); value.to_s; end
def Integer.from_json(value); value.to_i; end
def Float.from_json(value); value.to_f; end
def BigDecimal.from_json(value); BigDecimal.new(value.to_s); end
def Date.from_json(value); value.is_a?(Date) ? value : Date.parse(value); end
def Time.from_json(value); value.is_a?(Time) ? value : Time.parse(value); end


module TypeCaster
  # Also see: https://github.com/rails/rails/blob/master/activesupport/lib/active_support/concern.rb
  extend ActiveSupport::Concern
  
  module ClassMethods
    def field(name, fieldtype = String, options = {})
      attr_accessor name.to_sym
      (@fields ||= HashWithIndifferentAccess.new).merge!({name => options.merge(:type => fieldtype)})
    end
    
    def inherited(subclass)
      subclass.instance_variable_set("@fields", instance_variable_get("@fields").clone)
    end
    
  end
  
  module InstanceMethods
    
    def initialize(attrib = {})
      attrib = HashWithIndifferentAccess.new(attrib)
      attrib.stringify_keys!
      fields.each do |name, options|
        send("#{name}=", typecast(name,attrib[name.to_s]))
      end
    end

    def typecast(name, value)
      return fields[name.to_sym][:default] unless value
      fieldtype = fields[name.to_sym][:type] || String
      return fieldtype.from_json(value) unless value.is_a?(Array) || value.is_a?(Hash)
      begin
        klass = name.classify.constantize
        if value.is_a?(Array)
          coll = Array.new
          value.each do |v|
            coll << klass.new(v)
          end
          coll
        else
          klass.new(value)
        end
      rescue
        value
      end
    end

    def attributes
      @attributes ||= Hash[fields.keys.collect{|a| [a, self.send(a)]}]
    end
    
    def fields
      self.class.instance_variable_get("@fields")
    end
    
    
  end
  
end