Delete a key from a MongoDB document using Mongoos

问题:

I'm using the Mongoose Library for accessing MongoDB with node.js

Is there a way to remove a key from a document? i.e. not just set the value to null, but remove it?

User.findOne({}, function(err, user){
  //correctly sets the key to null... but it's still present in the document
  user.key_to_delete = null;

  // doesn't seem to have any effect
  delete user.key_to_delete;

  user.save();
});

回答1:

In early versions, you would have needed to drop down the node-mongodb-native driver. Each model has a collection object that contains all the methods that node-mongodb-native offers. So you can do the action in question by this:

User.collection.update({_id: user._id}, {$unset: {field: 1 }});

Since version 2.0 you can do:

User.update({_id: user._id}, {$unset: {field: 1 }}, callback);

And since version 2.4, if you have an instance of a model already you can do:

doc.field = undefined;
doc.save(callback);

回答2:

You'll want to do this:

User.findOne({}, function(err, user){
  user.key_to_delete = undefined;
  user.save();
});

回答3:

I use mongoose and using any of the above functions did me the requirement. The function compiles error free but the field would still remain.

user.set('key_to_delete', undefined, {strict: false} );

did the trick for me.

回答4:

At mongo syntax to delete some key you need do following:

{ $unset : { field : 1} }

Seems at Mongoose the same.

Edit

Check this example.

回答5:

Could this be a side problem like using

function (user)

instead of

function(err, user)

for the find's callback ? Just trying to help with this as I already had the case.

回答6:

Mongoose document is NOT a plain javascript object and that's why you can't use delete operator.(Or unset from 'lodash' library).

Your options are to set doc.path = null || undefined or to use Document.toObject() method to turn mongoose doc to plain object and from there use it as usual. Read more in mongoose api-ref: http://mongoosejs.com/docs/api.html#document_Document-toObject

Example would look something like this:

User.findById(id, function(err, user) {
    if (err) return next(err);
    let userObject = user.toObject();
    // userObject is plain object
});

回答7:

you can use delete user._doc.key