MongoDB-使用$ set更新子文档

Question

I have this document:

{ "data" : "AP1IUY9Bfp", "me" : { "something" : "somevalue" } }

I have this object:

webpage: 'stackoverflow'

How can I $push/$set this field into document.me, so the final result will equal:

{ "data" : "AP1IUY9Bfp", "me" : { "something" : "somevalue", "webpage": "stackoverflow" } }

If I try this using $set , like this:

db.collection('doc').update({id: 'AP1IUY9Bfp'}, {'$set': {'me': webpage: 'stackoverflow'}}

The result equals:

{ "data" : "AP1IUY9Bfp", "me" : { "webpage" : "stackoverflow" } }

(it overwrites the field)

Thanks!

Answer 1

What you'll want to do is something like this:

{'$set': {'me.webpage': 'stackoverflow'} }

Note the only difference is that I'm using dot notation to point to a sub-document.

Think about it as you would a normal JSON object outside of Mongo. You use dot notation to access properties of objects - mongo works the same way.

Here is a link to the relevant documentation regarding subdocuments and the dot notation in mongo - http://docs.mongodb.org/manual/core/document/#dot-notation

Dot Notation

MongoDB uses the dot notation to access the elements of an array and to access the fields of a subdocument.

...

To access a field of a subdocument with dot-notation, concatenate the subdocument name with the dot (.) and the field name, and enclose in quotes:

'<subdocument>.<field>'

Answer 2

一定不是

 db.collection('doc').update({id: 'AP1IUY9Bfp'}, {'me': $set: { webpage: 'stackoverflow'}}