Is a variable for a field name allowed during update in Meteor?

Question

I have been trying to update a collection i have.Problem is,i dont know the field name so am relying on some logic to come up with the field name.

For instance

  Er.update({ _id: "BCwrQEdiTr9GMmKWW" }, {
    $set: {
      "x" : y
    }
  });

where x is the field name.

This is my code

var obj = {};
obj[x] = y;

Er.update({ _id: "BCwrQEdiTr9GMmKWW" }, {$set: {obj}});

I am getting this error

update failed: MongoError: The dotted field 'ersubjects.0.English' in 'obj.ersubjects.0.English' is not valid for storage.

English is a field under ersubjects so i want to update it this way ersubjects.0.English and it works on mongo.

Why is this not working in meteor?.

Answer 1

You can't store documents that have a dot in the key. See this answer for an explanation.

What you can do is use lodash's extremely handy _.set function to create your object with dynamic keys like this:

var obj = {};
var variableKey = 'ersubjects';
_.set(obj, [variableKey, 0, 'English], 'someValue');

Now you can safely store this object to Mongo.