proof.rb

>> require 'mongo_mapper'
=> true
>> MongoMapper.database = 'itsatest'
=> "itsatest"
>> class Person
>>   include MongoMapper::Document
>>   key :first_key
>> end
=> #<MongoMapper::Key:0x101fe92a8 @name="first_key", @type=nil, @default_value=nil, @options={}>
>> first = Person.new(:first_key => 'first_value')
=> #<Person _id: nil, first_key: "first_value">
>> first.save
=> true
>> class Person
>>   key :second_key
>> end
=> #<MongoMapper::Key:0x101fd50c8 @name="second_key", @type=nil, @default_value=nil, @options={}>
>> Person.new
=> #<Person second_key: nil, _id: nil, first_key: nil>
>> first.second_key = 'second_value'
MongoMapper::KeyNotFound: Could not find key: "second_key"
	from /Library/Ruby/Gems/1.8/gems/mongo_mapper-0.6.8/lib/mongo_mapper/embedded_document.rb:361:in `read_attribute'
	from /Library/Ruby/Gems/1.8/gems/mongo_mapper-0.6.8/lib/mongo_mapper/dirty.rb:78:in `send'
	from /Library/Ruby/Gems/1.8/gems/mongo_mapper-0.6.8/lib/mongo_mapper/dirty.rb:78:in `clone_key_value'
	from /Library/Ruby/Gems/1.8/gems/mongo_mapper-0.6.8/lib/mongo_mapper/dirty.rb:118:in `write_attribute'
	from (eval):10:in `second_key='
	from (irb):13
>> first
=> #<Person _id: 4b3345d833e0ad021d000001, first_key: "first_value">
>> exit

$ irb
>> require 'mongoid'
=> true
>> connection = Mongo::Connection.new('localhost')
=> #<Mongo::Connection:...>
>> Mongoid.database = connection.db('anotherproof')
=> #<Mongo::DB:...>>
>> class Person < Mongoid::Document
>>   field :first_key
>> end
=> nil
>> first = Person.new(:first_key => 'first_value')
=> Person : {"_id"=>"4b33471633e0ad0227000001", "first_key"=>"first_value"}
>> first.save
=> Person : {"_id"=>"4b33471633e0ad0227000001", "first_key"=>"first_value"}
>> class Person < Mongoid::Document
>>   field :second_key
>> end
=> nil
>> first.second_key = 'second_value'
=> "second_value"
>> first.save
=> true
>> first
=> Person : {"second_key"=>"second_value", "_id"=>"4b33471633e0ad0227000001", "first_key"=>"first_value"}
>> exit