MongoDB Updating Entry in Array Within Document

This is done via the "$pop" operation but most examples out there operate on simple objects. Here's how it's done for an array that's deeper within the document.

So e.g. if we have a document like this in the "workshop" collection:

{ "_id" : ObjectId("51e216e55cf2ff1231dee123"), "info" : { "name" : “Workshop X”, "city" : “Sacramento” } "inventory" : { "cars" : [ { "licensePlate" : "XXXX01", "make" : “Toyota” }, { "licensePlate" : "XXXX02", "make" : “Kia” }, { "licensePlate" : "XXXX03", "make" : “Hyundai” }, { "licensePlate" : "XXXX04", "make" : “Nissan” }, { "licensePlate" : "XXXX05", "make" : “Honda” } ] } }

We could remove the entry at the bottom of the array with the command:

db.workshop.update({"info.name":"Workshop X"} ,{$pop:{"inventory.cars" : 1}});

Note that if you use the dot notation for accessing attributes deeper into the document, you'll need to surround the expression with quotes.

More documentation on $pop here: http://docs.mongodb.org/manual/reference/operator/update/pop/#up._S_pop