In former version of Mongoid I would write:
Clothes.where("$or" => [{"$and" => [{_type: "Shoes"}, {is_secondhand: false}]},
{"$and"=> [{_type: "Shirts"}, {is_secondhand: true}]}])
How should I write that in Mongoid 3.0.13?
You probably don’t need those ands.
Try this:
A lot has changed in Mongoid 3 and most of the querying selectors were moved to Origin. Have a look at the Origin documentation.