Advanced MongoDB operators in LoopBack 4

Question

Is it possible to use advanced MongoDB operators such as Array Update Operators within a Loopback 4 application?

Answer 1

Hello from the LoopBack team

We don't have a first-class support for executing custom MongoDB operators yet.

I see two possible solution:

• Execute such update command as a custom command. Unfortunately, this is not as straightforward as I would like it to be, see the GitHub issue loopback-next#3342 for more details. The current workaround is to call connector's execute method and manually convert it from callback-style to async/promise style.

  Example code based on https://github.com/strongloop/loopback-next/issues/2807#issuecomment-487590905:

  const repo = // obtain the repository instance, e.g. via @inject()
  const result = await new Promise((resolve, reject) => {
    repo.dataSource.connector.execute('MyCollection', 'update', {
      $push: {
        tags: ['new tag'] 
      }
    ],
    (err, data) => {
      if (err) reject(err);
      else resolve(data);
    });
  });
  

• Enhance LoopBack's Repository implementations to allow MongoDB update operators in the patch data. This feature is already supported by LoopBack 3 but we haven't exposed it in LoopBack 4 yet. Can you open a new GitHub issue please?