Allow removal of specific callbacks from query listeners

README.md

@@ -592,23 +592,33 @@ storageRef.downloadUrl()
 
 ### Realtime Database
 
-#### database attribute
-
 The native Firebase JavaScript library provides a featureful realtime database that works out of the box. Firestack provides an attribute to interact with the database without needing to configure the JS library.
 
+#### DatabaseRef
+
+Firestack attempts to provide the same API as the JS Firebase library for both Android and iOS platforms. [Check out the firebase guide](https://firebase.google.com/docs/database/web/read-and-write) for more information on how to use the JS library.
+
+#### Example
+
 ```javascript
-firestack.database
- .ref(LIST_KEY)
- .on('value', snapshot => {
- if (snapshot.val()) {
- console.log('The list was updated');
- }
- });
-```
 
-#### DatabaseRef
+function handleValueChange(snapshot) {
+ if (snapshot.val()) {
+ console.log('The list was updated');
+ }
+}
+
+const LIST_KEY = 'path/to/data';
+firestack.database.ref(LIST_KEY).on('value', handleValueChange);
 
-Firestack attempts to provide the same API as the JS Firebase library for both Android and iOS platforms.
+// Calling `.off` with a reference to the callback function will only remove that specific listener.
+// This is useful if multiple components are listening and unlistening to the same ref path.
+firestack.database.ref(LIST_KEY).off('value', handleValueChange);
+
+// Calling `.off` without passing the callback function will remove *all* 'value' listeners for that ref
+firestack.database.ref(LIST_KEY).off('value');
+
+```
 
 // TODO: Finish documenting
 

lib/modules/database.js

@@ -211,10 +211,14 @@ class DatabaseRef extends ReferenceBase {
  })
  }
 
- off(evt='') {
+ off(evt='', origCB) {
  const path = this.dbPath();
- return this.db.off(path, evt)
+ return this.db.off(path, evt, origCB)
  .then(({callback, subscriptions}) => {
+ if (dbSubscriptions[path][evt].length > 0) {
+ return subscriptions;
+ }
+
  return promisify('off', FirestackDatabase)(path, evt)
  .then(() => {
  // subscriptions.forEach(sub => sub.remove());
@@ -432,15 +436,20 @@ export class Database extends Base {
  return Promise.resolve({callback, subscriptions});
  }
 
- off(path, evt) {
+ off(path, evt, origCB) {
  const key = this._pathKey(path);
  // Remove subscription
  if (dbSubscriptions[key]) {
  if (!evt || evt === "") {
  dbSubscriptions[key] = {};
  } else if (dbSubscriptions[key][evt]) {
- delete dbSubscriptions[key][evt];
+ if (origCB) {
+ dbSubscriptions[key][evt].splice(dbSubscriptions[key][evt].indexOf(origCB), 1);
+ } else {
+ delete dbSubscriptions[key][evt];
+ }
  }
+
  if (Object.keys(dbSubscriptions[key]).length <= 0) {
  // there are no more subscriptions
  // so we can unwatch