New method: [YapDatabaseReadWriteTransaction addCompletionQueue:completionBlock:]

YapDatabase/Internal/YapDatabasePrivate.h

@@ -457,6 +457,9 @@ static NSString *const ext_key_class = @"class";
 
 @interface YapDatabaseReadWriteTransaction () {
 @public
+	NSMutableArray<dispatch_queue_t> *completionQueueStack;
+	NSMutableArray<dispatch_block_t> *completionBlockStack;
+	
 	BOOL rollback;
 	id customObjectForNotification;
 }

YapDatabase/YapDatabaseConnection.m

@@ -1963,6 +1963,18 @@ static int connectionBusyHandler(void *ptr, int count)
 			block(transaction);
 			[self postReadWriteTransaction:transaction];
 			
+			if (transaction->completionBlockStack)
+			{
+				NSUInteger count = transaction->completionBlockStack.count;
+				for (NSUInteger i = 0; i < count; i++)
+				{
+					dispatch_queue_t stackItemQueue = transaction->completionQueueStack[i];
+					dispatch_block_t stackItemBlock = transaction->completionBlockStack[i];
+					
+					dispatch_async(stackItemQueue, stackItemBlock);
+				}
+			}
+			
 		}}); // End dispatch_sync(database->writeQueue)
 		
 	}); // End dispatch_sync(connectionQueue)
@@ -2144,6 +2156,18 @@ static int connectionBusyHandler(void *ptr, int count)
 			block(transaction);
 			[self postReadWriteTransaction:transaction];
 			
+			if (transaction->completionBlockStack)
+			{
+				NSUInteger count = transaction->completionBlockStack.count;
+				for (NSUInteger i = 0; i < count; i++)
+				{
+					dispatch_queue_t stackItemQueue = transaction->completionQueueStack[i];
+					dispatch_block_t stackItemBlock = transaction->completionBlockStack[i];
+					
+					dispatch_async(stackItemQueue, stackItemBlock);
+				}
+			}
+			
 			if (completionBlock)
 				dispatch_async(completionQueue, completionBlock);
 			

YapDatabase/YapDatabaseTransaction.h

@@ -783,6 +783,21 @@ NS_ASSUME_NONNULL_BEGIN
 **/
 - (void)removeAllObjectsInAllCollections;
 
+#pragma mark Completion
+
+/**
+ * It's often useful to compose code into various reusable functions which take a
+ * YapDatabaseReadWriteTransaction as a parameter. However, the ability to compose code
+ * in this manner is often prevented by the need to perform a task after the commit has finished.
+ * 
+ * The end result is that programmers either end up copy-pasting code,
+ * or hack together a solution that involves functions returning completion blocks.
+ *
+ * This method solves the dilemma by allowing encapsulated code to register its own commit completionBlock.
+**/
+- (void)addCompletionQueue:(nullable dispatch_queue_t)completionQueue
+           completionBlock:(dispatch_block_t)completionBlock;
+
 @end
 
 NS_ASSUME_NONNULL_END

YapDatabase/YapDatabaseTransaction.m

@@ -5977,6 +5977,39 @@
 	}
 }
 
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+#pragma mark Completion
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * It's often useful to compose code into various reusable functions which take a
+ * YapDatabaseReadWriteTransaction as a parameter. However, the ability to compose code
+ * in this manner is often prevented by the need to perform a task after the commit has finished.
+ * 
+ * The end result is that programmers either end up copy-pasting code,
+ * or hack together a solution that involves functions returning completion blocks.
+ *
+ * This method solves the dilemma by allowing encapsulated code to register its own commit completionBlock.
+**/
+- (void)addCompletionQueue:(dispatch_queue_t)completionQueue
+           completionBlock:(dispatch_block_t)completionBlock
+{
+	if (completionBlock == nil)
+		return;
+	
+	if (completionQueue == nil)
+		completionQueue = dispatch_get_main_queue();
+	
+	if (completionQueueStack == nil)
+		completionQueueStack = [[NSMutableArray alloc] initWithCapacity:1];
+	
+	if (completionBlockStack == nil)
+		completionBlockStack = [[NSMutableArray alloc] initWithCapacity:1];
+	
+	[completionQueueStack addObject:completionQueue];
+	[completionBlockStack addObject:completionBlock];
+}
+
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 #pragma mark Extensions
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////