#14 does an empty query fire the onvalue function ?

Author: EddyVerbruggen

README.md

@@ -114,6 +114,9 @@ Let's say we have the structure as defined at `setValue`, then use this query to
         onQueryEvent,
         "/companies",
         {
+            // set this to true if you want to check if the value exists or just want the event to fire once
+            // default false, so it listens continuously
+            singleEvent: true,
             // order by company.country
             orderBy: {
                 type: firebase.QueryOrderByType.CHILD,

firebase-common.d.ts

@@ -13,15 +13,15 @@ declare module "nativescript-plugin-firebase" {
        */
       PASSWORD
     }
-    
+
     /**
      * The allowed values for QueryOptions.orderBy.type.
      */
     enum QueryOrderByType {
       KEY,
       VALUE,
       CHILD,
-      PRIORITY    
+      PRIORITY
     }
 
     /**
@@ -30,7 +30,7 @@ declare module "nativescript-plugin-firebase" {
     enum QueryRangeType {
       START_AT,
       END_AT,
-      EQUAL_TO   
+      EQUAL_TO
     }
 
     /**

firebase.android.js

@@ -305,7 +305,21 @@ firebase.query = function (updateCallback, path, options) {
         }
       }
 
-      firebase._addObservers(query, updateCallback);
+      if (options.singleEvent) {
+        var listener = new com.firebase.client.ValueEventListener({
+          onDataChange: function (snapshot) {
+            updateCallback(firebase.getCallbackData('ValueChanged', snapshot));
+          },
+          onCancelled: function (firebaseError) {
+            updateCallback({
+              error: firebaseError.getMessage()
+            });
+          }
+        });
+        query.addListenerForSingleValueEvent(listener);
+      } else {
+        firebase._addObservers(query, updateCallback);
+      }
       resolve();
     } catch (ex) {
       console.log("Error in firebase.query: " + ex);

firebase.d.ts

@@ -41,6 +41,14 @@ declare module "nativescript-plugin-firebase" {
         type: QueryLimitType;
         value: number;
       };
+
+      /**
+       * Set this to true if you don't want to listen for any future updates,
+       * but just want to retrieve the current value.
+       * You can also use this to check if certain data is in the database.
+       * Default false.
+       */
+      singleEvent?: boolean;
     }
 
     /**
@@ -70,7 +78,7 @@ declare module "nativescript-plugin-firebase" {
       email: string;
       password: string;
     }
-    
+
     /**
      * The returned object in the callback handlers
      * of the addChildEventListener and addValueEventListener functions.

firebase.ios.js

@@ -268,7 +268,13 @@ firebase.query = function (updateCallback, path, options) {
         }
       }
 
-      firebase._addObservers(query, updateCallback);
+      if (options.singleEvent) {
+        query.observeSingleEventOfTypeWithBlock(FEventType.FEventTypeValue, function (snapshot) {
+          updateCallback(firebase.getCallbackData('ValueChanged', snapshot));
+        });
+      } else {
+        firebase._addObservers(query, updateCallback);
+      }
       resolve();
     } catch (ex) {
       console.log("Error in firebase.query: " + ex);

package.json

@@ -1,6 +1,6 @@
 {
   "name": "nativescript-plugin-firebase",
-  "version": "2.0.0",
+  "version": "2.0.1",
   "description" : "Fire. Base. Firebase!",
   "main" : "firebase.js",
   "nativescript": {