How can I find embedded Mongoid documents based on multiple criteria?

问题

I have a Mongoid document with embedded documents in it. I want to search the top-level documents for all of them where there is an embedded document that has multiple criteria.

TopDoc.where('inside.first_name' => 'Bob', 'inside.last_name' => 'Jones')

But it seems to me this would match on a TopDoc with Bob Wever and Paul Jones, which is wrong.

回答1:

You need to use $elemMatch. With Mongoid, the following line should do the trick

TopDoc.elem_match(inside: { first_name: 'Bob', last_name: 'Jones' })

which is equivalent to :

TopDoc.where(:inside.elem_match => { first_name: 'Bob', last_name: 'Jones'})

来源：https://stackoverflow.com/questions/15034489/how-can-i-find-embedded-mongoid-documents-based-on-multiple-criteria