在RealTime数据库上删除数据-Firebase

Question

I'm using firebase realtime database and has following rules setup for the database,

{
  "rules": {
    ".read": "auth !== null",
    ".write": "auth !== null"
  }
}

But when I try to delete an entry, it gives me an error saying permission denied as follows.

Database: Client doesn't have permission to access the desired data. (database/permission-denied).

What should I do? I can't understand why I can do all the reads and writes pretty oki with the current rules and not delete.

Can anyone help me with this?

Note: Image of the results related to the Firebase Simulator

When checked for the firebase.auth().currentUser :

deleteUserAccount(userId) {
 let knownLocationRef = this.database.ref('lastKnown/' + userId);
 let promises = [];
 console.log('auth details', this.auth.currentUser);
 console.log('auth details null', this.auth.currentUser !== null); //returns true
         knownLocationRef.once('value').then( (data) => {
            console.log('data ', data.val());
            if (data.val() !== null) {
                let prevLat = data.val().lat;
                let prevLong = data.val().long;
                console.log('auth details', this.auth.currentUser);
                console.log('auth details null', this.auth.currentUser !== null); //returns false
                promises.push(knownLocationRef.remove());
            }
        });
         return Promise.all(promises);
 }

Answer 1

Here are some issues with your code and how you are handling promises:

function deleteUserAccount(userId) {
  let knownLocationRef = this.database.ref('lastKnown/' + userId);
  let promises = []; // good idea for collecting a list of distinct 
                     // promises, maybe not here

  // This is a promise, 'then' is a continuation from which you can return 
  // either a data result or another promise
  knownLocationRef.once('value').then((data) => {
    // if data is valid, return another promise
    if (data.val() !== null) {
      // ...

      // If you were looping and collecting promises, then this might help, 
      // but you don't want to collect inner promises.
      promises.push(knownLocationRef.remove());
    }
  });

  // This returns before everything in `.then` executes
  return Promise.all(promises);
}

Here's a fixed version:

function deleteUserAccount(userId) {
  let knownLocationRef = this.database.ref('lastKnown/' + userId);
  let promises = []; // For the sake of argument, I will use this to collect 
                     // outer promises.

  // normally I would return here, but as an example, I'll uses the 
  // promises array
  promises.push(knownLocationRef.once('value').then((data) => {
    // if data is valid, return another promise
    if (data.val() !== null) {
      // ...

      // Return a Promise from a promise
      return knownLocationRef.remove();
    }

    return null; // no data to process
  }));

  // wait on outer promises
  return Promise.all(promises)
    .catch(console.log); // log errors from any promise
}

Here is a version without the extra promises array.

function deleteUserAccount(userId) {
  let knownLocationRef = this.database.ref('lastKnown/' + userId);

  return knownLocationRef.once('value')
    .then((data) => {
      // if data is valid, return another promise
      if (data.val() !== null) {

        // Return a Promise from a promise
        return knownLocationRef.remove();
      }

      return null; // no data to process
    })
    .catch(console.log);
}