Observing Firebase data retrieval in an AngularJS application

Question

Observing Firebase data retrieval in an AngularJS application

Currently, I am developing an Angular application integrated with Firebase, and one of the features I'm working on is a one-to-one chat system. My goal is to check if a chat room already exists between the user using the application and the person they want to chat with by querying Firebase. If the room exists, I intend to assign that specific room as the selected room within the scope. To achieve this, I am utilizing the "Messages" service to execute the query.

this.roomQuery = function(user1ID, user2ID) {
  roomsRef.orderByChild("user1").equalTo(user1ID).on("child_added", function(snapshot) {

    if (snapshot.val().user2 == user2ID) {
      self.selectedRoom = snapshot.key();
      console.log(self.selectedRoom);
    } else {
      self.selectedRoom = null;
    }
  
  })
}

In my controller, I have incorporated the following:

$scope.$watch(
    function(){ return Messages.selectedRoom },
      
    function(newValue, oldValue) {
      $scope.selectedRoom = newValue;
    }
    )

Typically, the $scope.$watch method has been effective in updating values, yet it occasionally fails in this scenario. Although the console consistently displays the correct value for Messages.selectedRoom, there are instances where $scope.selectedRoom does not reflect the update. This discrepancy leaves me puzzled. Shouldn't the log appearing correctly imply that the scope has also been updated?

javascript angularjs firebase angularfire

Answer 1

Answer №1

When working with Angular, it's important to note that the $digest function may not be aware of when a Firebase query is completed. To simplify this process, consider using AngularFire.

this.roomQuery = function(user1ID, user2ID) {
  var query = roomsRef.orderByChild("user1").equalTo(user1ID);
  return $firebaseObject(query).$loaded();
};

this.roomQuery("1", "2")
  .then(function(data) {
    // perform any necessary checks here
  });

The $firebaseObject() function automatically handles digest calls for you when given a reference or query.

If you're interested, look into implementing resolve in your router to inject the roomQuery, which returns a promise with .$loaded().

Answer 2

When working with Angular, it's important to note that the $digest function may not be aware of when a Firebase query is completed. To simplify this process, consider using AngularFire.

this.roomQuery = function(user1ID, user2ID) {
  var query = roomsRef.orderByChild("user1").equalTo(user1ID);
  return $firebaseObject(query).$loaded();
};

this.roomQuery("1", "2")
  .then(function(data) {
    // perform any necessary checks here
  });

The $firebaseObject() function automatically handles digest calls for you when given a reference or query.

If you're interested, look into implementing resolve in your router to inject the roomQuery, which returns a promise with .$loaded().

Answer 3

Answer №2

David helped me find the solution I was looking for. If anyone is facing a similar issue, here is how I managed to solve it:

this.customRoomQuery = function(userOne, userTwo) {
  var specificQuery = roomsRef.orderByChild("user1").equalTo(userOneID)

  return $firebaseArray(specificQuery).$loaded();
}

Instead of using Object, I opted for $firebaseArray and in my controller:

$scope.fetchCustomRoom = function() {
    Messages.customRoomQuery($scope.userOne.id, $scope.userTwo.$id).then(function(data)
    {
      $scope.data = data;
      for(var i=0, length = data.length; i < length; i++){
        if (data[i].user2 == $scope.userTwo.$id) {
          $scope.selectedRoom = data[i].$id;
        }
      }
    }
    )
  }

I apologize for any confusion caused by the variable names – I modified them for clarity within this post.

Answer 4

David helped me find the solution I was looking for. If anyone is facing a similar issue, here is how I managed to solve it:

this.customRoomQuery = function(userOne, userTwo) {
  var specificQuery = roomsRef.orderByChild("user1").equalTo(userOneID)

  return $firebaseArray(specificQuery).$loaded();
}

Instead of using Object, I opted for $firebaseArray and in my controller:

$scope.fetchCustomRoom = function() {
    Messages.customRoomQuery($scope.userOne.id, $scope.userTwo.$id).then(function(data)
    {
      $scope.data = data;
      for(var i=0, length = data.length; i < length; i++){
        if (data[i].user2 == $scope.userTwo.$id) {
          $scope.selectedRoom = data[i].$id;
        }
      }
    }
    )
  }

I apologize for any confusion caused by the variable names – I modified them for clarity within this post.

Observing Firebase data retrieval in an AngularJS application

Answer №1

Answer №2

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