gistfile1.rb

1.9.3p194 :008 > Atm.create! :name => 'td'
 => #<Atm _id: 50da19f3803a9372a4000001, name: "td", _type: "Atm"> 
1.9.3p194 :009 > Item.create! :name => 'item'
 => #<Item _id: 50da19fb803a9372a4000002, name: "item", _type: "Item"> 
1.9.3p194 :010 > Item.all.map &:_type
 => ["Atm", "Item"] 
1.9.3p194 :011 > Item.all
 => #<Mongoid::Criteria
  selector: {}
  options:  {}
  class:    Item
  embedded: false>
 
1.9.3p194 :012 > Item.all.map &:_type
 => ["Atm", "Item"] 
1.9.3p194 :013 > Atm.all.map &:_type
 => ["Atm"] 
1.9.3p194 :014 > Item.all.map &:_type
 => ["Atm", "Item"] 
1.9.3p194 :015 > Item.ne(_type: 'Atm').map &:_type
 => ["Item"] 
1.9.3p194 :016 > 
1.9.3p194 :017 >   Item.where(_type: 'Item').map &:_type
 => ["Item"]