fix(database): only update observers on unique value

fixes: #20

src/afo-list-observable.ts

@@ -18,6 +18,10 @@ export class AfoListObservable<T> extends ReplaySubject<T> {
    * The current value of the {@link AfoListObservable}
    */
   value: any;
+  /**
+   * The value preceding the current value.
+   */
+  private previousValue: any;
   /**
    * Creates the {@link AfoListObservable}
    * @param ref a reference to the related FirebaseListObservable
@@ -63,6 +67,15 @@ export class AfoListObservable<T> extends ReplaySubject<T> {
       }
     });
   }
+  /**
+   * Only calls next if the new value is unique
+   */
+  uniqueNext(newValue) {
+    if (JSON.stringify(this.previousValue) !== JSON.stringify(newValue) ) {
+      this.previousValue = newValue;
+      this.next(newValue);
+    }
+  }
   /**
    * Wraps the AngularFire2 FirebaseListObservable [push](https://goo.gl/nTe7C0) method
    *
@@ -186,6 +199,6 @@ export class AfoListObservable<T> extends ReplaySubject<T> {
    * Sends the the current {@link value} to all subscribers
    */
   private updateSubscribers() {
-    this.next(this.value);
+    this.uniqueNext(this.value);
   }
 }

src/afo-object-observable.ts

@@ -18,6 +18,10 @@ export class AfoObjectObservable<T> extends ReplaySubject<T> {
    * The current value of the {@link AfoObjectObservable}
    */
   value: any;
+  /**
+   * The value preceding the current value.
+   */
+  private previousValue: any;
   /**
    * Creates the {@link AfoObjectObservable}
    * @param ref a reference to the related FirebaseObjectObservable
@@ -106,6 +110,15 @@ export class AfoObjectObservable<T> extends ReplaySubject<T> {
     this.offlineWrite(promise, 'update', [value]);
     return promise;
   }
+  /**
+   * Only calls next if the new value is unique
+   */
+  uniqueNext(newValue) {
+    if (JSON.stringify(this.previousValue) !== JSON.stringify(newValue) ) {
+      this.previousValue = newValue;
+      this.next(newValue);
+    }
+  }
   /**
    * Convenience method to save an offline write
    *
@@ -142,6 +155,6 @@ export class AfoObjectObservable<T> extends ReplaySubject<T> {
    * Sends the the current {@link value} to all subscribers
    */
   private updateSubscribers() {
-    this.next(unwrap(this.ref.$ref.key, this.value, () => this.value !== null));
+    this.uniqueNext(unwrap(this.ref.$ref.key, this.value, () => this.value !== null));
   }
 }

src/database.ts

@@ -149,7 +149,7 @@ export class AngularFireOfflineDatabase {
           if (this.processing.current) {
             this.processing.listCache[key] = cacheValue;
           } else {
-            this.listCache[key].sub.next(cacheValue);
+            this.listCache[key].sub.uniqueNext(cacheValue);
           }
         });
       }
@@ -162,7 +162,7 @@ export class AngularFireOfflineDatabase {
     this.processing.current = false;
     ['list', 'object'].forEach(type => {
       Object.keys(this.processing[`${type}Cache`]).forEach(cacheKey => {
-        this[`${type}Cache`][cacheKey].sub.next( this.processing[`${type}Cache`][cacheKey] );
+        this[`${type}Cache`][cacheKey].sub.uniqueNext( this.processing[`${type}Cache`][cacheKey] );
       });
     });
   }
@@ -193,7 +193,7 @@ export class AngularFireOfflineDatabase {
       if (this.processing.current) {
         this.processing.objectCache[key] = cacheValue;
       } else {
-        this.objectCache[key].sub.next( cacheValue );
+        this.objectCache[key].sub.uniqueNext( cacheValue );
       }
       this.localForage.setItem(`read/object${key}`, snap.val());
     });
@@ -204,7 +204,7 @@ export class AngularFireOfflineDatabase {
         if (this.processing.current) {
           this.processing.objectCache[key] = cacheValue;
         } else {
-          this.objectCache[key].sub.next( cacheValue );
+          this.objectCache[key].sub.uniqueNext( cacheValue );
         }
       }
     });
@@ -276,7 +276,7 @@ export class AngularFireOfflineDatabase {
       if (this.processing.current) {
         this.processing.listCache[key] = cacheValue;
       } else {
-        this.listCache[key].sub.next( cacheValue );
+        this.listCache[key].sub.uniqueNext( cacheValue );
       }
       this.setList(key, value);
     });

tests/afo-list-observable.spec.ts

@@ -200,7 +200,7 @@ describe('List Observable', () => {
       expect(x[0].$exists()).toBe(true);
       done();
     });
-    listObservable.next([]);
+    listObservable.uniqueNext([]);
   });
 });
 

tests/afo-object-observable.spec.ts

@@ -86,7 +86,7 @@ describe('Object Observable', () => {
         done();
       }
     });
-    objectObservable.next('a value');
+    objectObservable.uniqueNext('a value');
   });
 
   it('should emulate a que for update', done => {
@@ -107,7 +107,7 @@ describe('Object Observable', () => {
         done();
       }
     });
-    objectObservable.next({
+    objectObservable.uniqueNext({
       title: 'old title',
       key2: 'other value'
     });