Updating MongoDB object field

Question

I have searched and tried many answers but I can't seem to get this working. I have a user in MongoDB (db.users...) and I'm trying to update a field titled 'role' in one particular document. If I perform a :

db.users.find();

I get:

{ "_id" : "fDx2g34G8vxsDu3vf", "createdAt" : ISODate("2014-06-03T16:31:47.382Z"), 
  "emails" : [  {  "address" : "[email protected]",  "verified" : false } ], 
  "profile" : { "name" : "Admin", "role" : "user", "division" : "0", "enrolled" : "false" }, 
  "services" : { "password" : { "srp" : { "identity" "dEad06c_5mjzsprUzgRyh6tB66OiaybdLzbnxFzO1xh",
  "salt" : "zqWsh etc etc

Which is fine, if I then perform a:

db.users.update({_id:"2xnoy3jqcHCaFp7Br"}, { role:"admin"});

I get a:

assert failed : need an object Error: Printing Stack Trace at printStackTrace (src/mongo/shell/utils.js:37:15) at doassert (src/mongo/shell/assert.js:6:5) at assert (src/mongo/shell/assert.js:14:5) at DBCollection.update (src/mongo/shell/collection.js:220:5) at (shell):1:10

Any ideas?

Thanks.

Answer 1

First of all if you are trying to update the role field of the profile subdocument your syntax is off. It should be:

db.users.update({_id:"2xnoy3jqcHCaFp7Br"}, {$set: { "profile.role":"admin"}})

Otherwise you will just delete all the other fields of the document.

Regarding the error message, that normally only occurs when you run update with a single argument (the query) without the fields to update. Are you sure you are calling it as documented in your question?

Regardless I would highly advise you to review MongoDB documentation for updates:

http://docs.mongodb.org/manual/tutorial/modify-documents/