MongoDB - Removing ($unset) nested key from object when nested key is a variable

Question

Consider this document of lesson start times for the instructor Johnny Appleseed:

{
  _id: 'ka83nala9cya9epsj',
  fullName: Johnny Appleseed,
  schedule: {
   '11/05/2016': '12:30',
   '11/15/2016': '2:30',
   '11/16/2016': '1:30',
   '12/07/2016': '9:30',
   '12/18/2016': '10:30', 
   '12/23/2016': '8:30',
  }
  ...
}

We'll also have a function to handle all of this greatness. I've tried a few different mongo.update() combinations and nothing seems to be quite right. Here's an example on what I thought would of work but still doesn't.

function removeStartTime(_instrName, _lessonDate) {
  const _scheduleKey = `schedule.${_lessonDate}`;
  return Instructors.update({ fullName: _instrName }, { $unset: { _scheduleKey: 1 } });
}

The Goal:

Unschedule (remove) Johnny Appleseed from the scheduled 12/18/2016 date so the finished document will look like this:

{
  _id: 'ka83nala9cya9epsj',
  fullName: Johnny Appleseed,
  schedule: {
   '11/05/2016': '12:30',
   '11/15/2016': '2:30',
   '11/16/2016': '1:30',
   '12/07/2016': '9:30',
   '12/23/2016': '8:30',
  }
  ...
}

Please help and thanks!

JohnnyHK · Accepted Answer · 2016-12-18 17:30:52Z

2

You need to use the computed property name syntax when using a variable as a property name by surrounding it in square brackets:

Instructors.update({ fullName: _instrName }, { $unset: { [_scheduleKey]: 1 } });

answered Dec 18, 2016 at 17:30

JohnnyHK

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1 Comment

WizzyBoom Over a year ago

Works like a charm! Thank you. I've used computed property name syntax several times before but always in this obj[key] = 'someValue'; context, never wrapped then entire variable in square brackets before, which now makes plenty of since in a hand-slap-to-the-forehead sort of way. :) Thanks again.

Barney · Accepted Answer · 2016-12-18 17:20:13Z

0

Instructors.update({fullName: _instrName},{"$unset": {"schedule.12/18/2016": ""} })

answered Dec 18, 2016 at 17:20

Barney

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1 Comment

ad absurdum Over a year ago

This may answer the question, but is not as helpful as it could be. Please explain what was wrong with OPs code, why your changes worked, and possibly how your solution differs from the other solutions here.

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