add support for batching updates

firebase · Jan 3, 2017 · 4cf3b1e · 4cf3b1e
1 parent 4b7a264
commit 4cf3b1e
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Showing 7 changed files with 117 additions and 14 deletions.
diff --git a/FirebaseDatabaseUI/FUIArray.h b/FirebaseDatabaseUI/FUIArray.h
@@ -43,7 +43,8 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  * FUIArray provides an array structure that is synchronized with a Firebase reference or
  * query. It is useful for building custom data structures or sources, and provides the base for
- * FirebaseDataSource.
+ * FirebaseDataSource. FUIArray maintains a large amount of internal state, and most of its methods
+ * are not thread-safe.
  */
 @interface FUIArray : NSObject <FUICollection>
 

diff --git a/FirebaseDatabaseUI/FUIArray.m b/FirebaseDatabaseUI/FUIArray.m
@@ -33,6 +33,14 @@ @interface FUIArray ()
  */
 @property (strong, nonatomic) NSMutableSet<NSNumber *> *handles;
 
+/**
+ * Set to YES when any event that isn't a value event is received; set
+ * back to NO when receiving a value event.
+ * Used to keep track of whether or not the array is updating so consumers
+ * can more easily batch updates.
+ */
+@property (nonatomic, assign) BOOL isSendingUpdates;
+
 @end
 
 @implementation FUIArray
@@ -68,53 +76,84 @@ - (void)dealloc {
 #pragma mark - Private API methods
 
 - (void)observeQuery {
-  if (self.handles.count == 4) { /* don't duplicate observers */ return; }
+  if (self.handles.count == 5) { /* don't duplicate observers */ return; }
   FIRDatabaseHandle handle;
   handle = [self.query observeEventType:FIRDataEventTypeChildAdded
       andPreviousSiblingKeyWithBlock:^(FIRDataSnapshot *snapshot, NSString *previousChildKey) {
+        [self didUpdate];
         [self insertSnapshot:snapshot withPreviousChildKey:previousChildKey];
       }
       withCancelBlock:^(NSError *error) {
-        if ([self.delegate respondsToSelector:@selector(array:queryCancelledWithError:)]) {
-          [self.delegate array:self queryCancelledWithError:error];
-        }
+        [self raiseError:error];
       }];
   [_handles addObject:@(handle)];
 
   handle = [self.query observeEventType:FIRDataEventTypeChildChanged
       andPreviousSiblingKeyWithBlock:^(FIRDataSnapshot *snapshot, NSString *previousChildKey) {
+        [self didUpdate];
         [self changeSnapshot:snapshot withPreviousChildKey:previousChildKey];
       }
       withCancelBlock:^(NSError *error) {
-        if ([self.delegate respondsToSelector:@selector(array:queryCancelledWithError:)]) {
-          [self.delegate array:self queryCancelledWithError:error];
-        }
+        [self raiseError:error];
       }];
   [_handles addObject:@(handle)];
 
   handle = [self.query observeEventType:FIRDataEventTypeChildRemoved
       andPreviousSiblingKeyWithBlock:^(FIRDataSnapshot *snapshot, NSString *previousSiblingKey) {
+        [self didUpdate];
         [self removeSnapshot:snapshot withPreviousChildKey:previousSiblingKey];
       }
       withCancelBlock:^(NSError *error) {
-        if ([self.delegate respondsToSelector:@selector(array:queryCancelledWithError:)]) {
-          [self.delegate array:self queryCancelledWithError:error];
-        }
+        [self raiseError:error];
       }];
   [_handles addObject:@(handle)];
 
   handle = [self.query observeEventType:FIRDataEventTypeChildMoved
       andPreviousSiblingKeyWithBlock:^(FIRDataSnapshot *snapshot, NSString *previousChildKey) {
+        [self didUpdate];
         [self moveSnapshot:snapshot withPreviousChildKey:previousChildKey];
       }
       withCancelBlock:^(NSError *error) {
-        if ([self.delegate respondsToSelector:@selector(array:queryCancelledWithError:)]) {
-          [self.delegate array:self queryCancelledWithError:error];
-        }
+        [self raiseError:error];
+      }];
+  [_handles addObject:@(handle)];
+
+  handle = [self.query observeEventType:FIRDataEventTypeValue
+      andPreviousSiblingKeyWithBlock:^(FIRDataSnapshot *snapshot, NSString *previousChildKey) {
+        [self didFinishUpdates];
+      }
+      withCancelBlock:^(NSError *error) {
+        [self raiseError:error];
       }];
   [_handles addObject:@(handle)];
 }
 
+// Must be called from every non-value event listener in order to work correctly.
+- (void)didUpdate {
+  if (self.isSendingUpdates) {
+    return;
+  }
+  self.isSendingUpdates = YES;
+  if ([self.delegate respondsToSelector:@selector(arrayDidBeginUpdates:)]) {
+    [self.delegate arrayDidBeginUpdates:self];
+  }
+}
+
+// Must be called from a value event listener.
+- (void)didFinishUpdates {
+  if (!self.isSendingUpdates) { /* This is probably an error */ return; }
+  self.isSendingUpdates = NO;
+  if ([self.delegate respondsToSelector:@selector(arrayDidEndUpdates:)]) {
+    [self.delegate arrayDidEndUpdates:self];
+  }
+}
+
+- (void)raiseError:(NSError *)error {
+  if ([self.delegate respondsToSelector:@selector(array:queryCancelledWithError:)]) {
+    [self.delegate array:self queryCancelledWithError:error];
+  }
+}
+
 - (void)invalidate {
   for (NSNumber *handle in _handles) {
     [_query removeObserverWithHandle:handle.unsignedIntegerValue];

diff --git a/FirebaseDatabaseUI/FUICollection.h b/FirebaseDatabaseUI/FUICollection.h
@@ -68,6 +68,16 @@ NS_ASSUME_NONNULL_BEGIN
 
 @optional
 
+/**
+ * Called before any other events are sent.
+ */
+- (void)arrayDidBeginUpdates:(id<FUICollection>)collection;
+
+/**
+ * Called after all updates have finished.
+ */
+- (void)arrayDidEndUpdates:(id<FUICollection>)collection;
+
 /**
  * Delegate method which is called whenever an object is added to an FUIArray.
  * On a FUIArray synchronized to a Firebase reference, this corresponds to an

diff --git a/FirebaseDatabaseUITests/FUIArrayTest.m b/FirebaseDatabaseUITests/FUIArrayTest.m
@@ -443,4 +443,37 @@ - (void)testArrayMovesElementToStartWithNilPreviousKey {
     XCTAssert(expectedParametersWereCorrect, @"unexpected parameter in delegate callback");
 }
 
+- (void)testArraySendsMessageBeforeAnyUpdates {
+  __block NSInteger started = 0;
+  self.arrayDelegate.didStartUpdates = ^{
+    started++; // expect this to only ever be incremented once.
+  };
+  [self.observable populateWithCount:10];
+
+  XCTAssert(started == 1, @"expected array to start updates exactly once");
+
+  // Send a value event to mark the end of batch updates.
+  [self.observable sendEvent:FIRDataEventTypeValue withObject:nil previousKey:nil error:nil];
+}
+
+- (void)testArraySendsMessagesAfterReceivingValueEvent {
+  __block NSInteger started = 0;
+  self.arrayDelegate.didStartUpdates = ^{
+    started++; // expect this to only ever be incremented once.
+  };
+  [self.observable populateWithCount:10];
+
+  XCTAssert(started == 1, @"expected array to start updates exactly once");
+
+  __block NSInteger ended = 0;
+  self.arrayDelegate.didEndUpdates = ^{
+    ended++;
+  };
+
+  // Send a value event to mark the end of batch updates.
+  [self.observable sendEvent:FIRDataEventTypeValue withObject:nil previousKey:nil error:nil];
+
+  XCTAssert(ended == 1, @"expected array to end updates exactly once");
+}
+
 @end
diff --git a/FirebaseDatabaseUITests/FUIDatabaseTestUtils.h b/FirebaseDatabaseUITests/FUIDatabaseTestUtils.h
@@ -92,6 +92,8 @@ NS_ASSUME_NONNULL_BEGIN
 @end
 
 @interface FUIArrayTestDelegate : NSObject <FUICollectionDelegate>
+@property (nonatomic, copy) void (^didStartUpdates)();
+@property (nonatomic, copy) void (^didEndUpdates)();
 @property (nonatomic, copy) void (^queryCancelled)(id<FUICollection> array, NSError *error);
 @property (nonatomic, copy) void (^didAddObject)(id<FUICollection> array, id object, NSUInteger index);
 @property (nonatomic, copy) void (^didChangeObject)(id<FUICollection> array, id object, NSUInteger index);

diff --git a/FirebaseDatabaseUITests/FUIDatabaseTestUtils.m b/FirebaseDatabaseUITests/FUIDatabaseTestUtils.m
@@ -218,6 +218,18 @@ - (void)populateWithCount:(NSUInteger)count {
 
 @implementation FUIArrayTestDelegate
 
+- (void)arrayDidBeginUpdates:(id<FUICollection>)collection {
+  if (self.didStartUpdates != NULL) {
+    self.didStartUpdates();
+  }
+}
+
+- (void)arrayDidEndUpdates:(id<FUICollection>)collection {
+  if (self.didEndUpdates != NULL) {
+    self.didEndUpdates();
+  }
+}
+
 - (void)array:(id<FUICollection>)array didAddObject:(id)object atIndex:(NSUInteger)index {
   if (self.didAddObject != NULL) {
     self.didAddObject(array, object, index);

diff --git a/FirebaseUI.xcodeproj/project.pbxproj b/FirebaseUI.xcodeproj/project.pbxproj
@@ -10,6 +10,9 @@
 		8D01FC7B1DAEC2FF00BD7848 /* FUIIndexCollectionViewDataSourceTest.m in Sources */ = {isa = PBXBuildFile; fileRef = 8D01FC7A1DAEC2FF00BD7848 /* FUIIndexCollectionViewDataSourceTest.m */; };
 		8D1E107C1DAEB97300AEFCA0 /* FUIIndexTableViewDataSourceTest.m in Sources */ = {isa = PBXBuildFile; fileRef = 8D1E107B1DAEB97300AEFCA0 /* FUIIndexTableViewDataSourceTest.m */; };
 		8D2A84AA1D678B2B0058DF04 /* FirebaseUI.h in Headers */ = {isa = PBXBuildFile; fileRef = 8D2A84A91D678B2B0058DF04 /* FirebaseUI.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		8D306BBF1E1C64E200A13B0E /* FUIArrayTest.m in Sources */ = {isa = PBXBuildFile; fileRef = 8DA941E91D67951B00CD3685 /* FUIArrayTest.m */; };
+		8D306BC01E1C64F000A13B0E /* FUICollectionViewDataSourceTest.m in Sources */ = {isa = PBXBuildFile; fileRef = 8DA941EC1D67951B00CD3685 /* FUICollectionViewDataSourceTest.m */; };
+		8D306BC11E1C64F200A13B0E /* FUITableViewDataSourceTest.m in Sources */ = {isa = PBXBuildFile; fileRef = 8DA941ED1D67951B00CD3685 /* FUITableViewDataSourceTest.m */; };
 		8D3A120E1DC2B122007558BA /* FUISortedArray.h in Headers */ = {isa = PBXBuildFile; fileRef = 8D3A120C1DC2B122007558BA /* FUISortedArray.h */; };
 		8D3A120F1DC2B122007558BA /* FUISortedArray.m in Sources */ = {isa = PBXBuildFile; fileRef = 8D3A120D1DC2B122007558BA /* FUISortedArray.m */; };
 		8D78AF061D9D8CB000CFA9C5 /* UIImageView+FirebaseStorage.m in Sources */ = {isa = PBXBuildFile; fileRef = 8D7AD9B61D9317FB006866B9 /* UIImageView+FirebaseStorage.m */; };
@@ -1919,6 +1922,9 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				8D306BC01E1C64F000A13B0E /* FUICollectionViewDataSourceTest.m in Sources */,
+				8D306BC11E1C64F200A13B0E /* FUITableViewDataSourceTest.m in Sources */,
+				8D306BBF1E1C64E200A13B0E /* FUIArrayTest.m in Sources */,
 				8D01FC7B1DAEC2FF00BD7848 /* FUIIndexCollectionViewDataSourceTest.m in Sources */,
 				8D1E107C1DAEB97300AEFCA0 /* FUIIndexTableViewDataSourceTest.m in Sources */,
 				8D924C611DA6F69100C4DA48 /* FUIIndexArrayTest.m in Sources */,