Rails ActiveRecord #composed_of macro

1_models.rb

# == Schema Information
#
# Table name: blocks
#
#  id         :integer          not null, primary key
#  name       :string(255)
#  content    :text
#  type       :string(255)
#  created_at :datetime
#  updated_at :datetime
#
class Block < ActiveRecord::Base; end
  
# == Schema Information
#
# Table name: blocks
#
#  id         :integer          not null, primary key
#  name       :string(255)
#  content    :text
#  type       :string(255)
#  created_at :datetime
#  updated_at :datetime
#
class DateBlock < Block

  # Define a virtual attribute ':date' that maps to the real ':content' field
  # which is then serialized when persisted. Form fields are set up using
  # the :date attr but front end content call :content or :date, both
  # return a Date object.
  composed_of :date,
    class_name: 'Date',
    mapping: %w(content to_date),
    constructor: Proc.new { |date| date }
    
  serialize :content
end

2_block.log

2.1.3 :033 >   block = Block.new
 => #<Block id: nil, name: nil, content: nil, type: nil, created_at: nil, updated_at: nil> 
2.1.3 :034 > block.content
 => nil 
2.1.3 :035 > block.content = Date.today
 => Tue, 21 Oct 2014 
2.1.3 :036 > block.save
   (0.2ms)  begin transaction
  SQL (1.3ms)  INSERT INTO "blocks" ("content", "created_at", "updated_at") VALUES (?, ?, ?)  [["content", "2014-10-21"], ["created_at", "2014-10-21 20:33:10.755853"], ["updated_at", "2014-10-21 20:33:10.755853"]]
   (1.0ms)  commit transaction
 => true 
2.1.3 :037 > block.reload
  Block Load (0.4ms)  SELECT  "blocks".* FROM "blocks"  WHERE "blocks"."id" = ? LIMIT 1  [["id", 5]]
 => #<Block id: 5, name: nil, content: "2014-10-21", type: nil, created_at: "2014-10-21 20:33:10", updated_at: "2014-10-21 20:33:10"> 
2.1.3 :038 > block.content
 => "2014-10-21" 
2.1.3 :039 > block.content.class
 => String 
2.1.3 :040 > block.content < Date.today + 1.day
ArgumentError: comparison of String with Date failed

3_date_block.log

2.1.3 :071 >   block = DateBlock.new
 => #<DateBlock id: nil, name: nil, content: nil, type: "DateBlock", created_at: nil, updated_at: nil> 
2.1.3 :072 > block.content
 => nil 
2.1.3 :073 > block.date
 => nil 
2.1.3 :074 > block.date = Date.today
 => Tue, 21 Oct 2014 
2.1.3 :075 > block.save
   (0.1ms)  begin transaction
  SQL (0.5ms)  INSERT INTO "blocks" ("content", "created_at", "type", "updated_at") VALUES (?, ?, ?, ?)  [["content", "--- 2014-10-21\n...\n"], ["created_at", "2014-10-21 20:37:24.481074"], ["type", "DateBlock"], ["updated_at", "2014-10-21 20:37:24.481074"]]
   (0.8ms)  commit transaction
 => true 
2.1.3 :076 > block.content
 => Tue, 21 Oct 2014 
2.1.3 :077 > block.date
 => Tue, 21 Oct 2014 
2.1.3 :078 > block.date.class
 => Date 
2.1.3 :079 > block.content.class
 => Date 
2.1.3 :080 >