10、Ruby DataMappers: 让 Ruby 与 MongoDB 携手共进

Ruby DataMappers: 让 Ruby 与 MongoDB 携手共进

1. 一步创建对象

原本分两步的操作可以一步完成，示例如下：

irb> Vehicle.create(resource: Ship.create(is_military: true))
 => #<Vehicle _id: 4f042de8fed0ebc4c5000004, _type: "Vehicle", 
resource_type: "Ship", resource_id: BSON::ObjectId('4f042de8fed0ebc
4c5000003'), terrain: nil, cost: nil, weight: nil, max_speed: nil>

但不能反向操作，例如：

irb> ship = Ship.create(:vehicle => Vehicle.create)
 => #<Ship _id: 4f042dd0fed0ebc4c5000002, _type: "Ship", is_military: 
nil, is_cruise: nil, missile_capable: nil, anti_aircraft: nil, number_
engines: nil> 
irb> Vehicle.last
 => #<Vehicle _id: 4f042dd0fed0ebc4c5000001, _type: "Vehicle", 
reso