objective-c-blocks

I'd like to use blocks, but it causes me a EXC_BAD_ACCESS after a few calls. My code: - (void) sendBasket { if (currentSendToBasketBlock != nil) { // there's already a webservice going... set the new one as waiting waitingSendToBasketBlock = ^ { WebServicesModel *webServicesModel = [[[WebServicesModel alloc] init] autorelease]; webServicesModel.delegate = self; [webServicesModel sendBasketToServer:currentBasket]; [self showBasketBackground]; }; [waitingSendToBasketBlock copy]; } else { currentSendToBasketBlock = ^ { WebServicesModel *webServicesModel = [[[WebServicesModel alloc] init]

I'm trying to get my head around how object lifetime and reference counting interact with code blocks. In the following code I'm just doing a simple animation that flashes as the top view on a UINavigationController's stack is swapped. The tricky part is that the popped view controller is the one where this code is defined . [UIView animateWithDuration:0.2 animations:^{self.navigationController.view.alpha = 0.0;} completion:^(BOOL finished){ UINavigationController *navController = self.navigationController; [self.navigationController popViewControllerAnimated:NO]; [navController

In my application, I let a progress indicator starts animation before I send a HTTP request. The completion handler is defined in a block. After I get the response data, I hide the progress indicator from inside the block. My question is, as I know, UI updates must be performed in the main thread. How can I make sure it? If I define a method in the window controller which updates UI, and let the block calls the method instead of updating UI directly, is it a solution? Also, if your app targets iOS >= 4 you can use Grand Central Dispatch: dispatch_async(dispatch_get_main_queue(), ^{ // This

The clang analyzer can check for returning stack-based memory. dispatch_block_t getPrintBlock (const char *msg) { return ^{ printf("%s", msg); }; } raises this error: returning block that lives on the local stack What does this error mean? You need to make a copy of the block to move it to the heap. i.e. something like: dispatch_block_t createPrintBlock (const char *msg) { return Block_copy(^{ printf("%s", msg); }) ; } CRD The error means you are returning a value which will be invalid after the method returns. This is not just an issue with blocks, consider: - (int *) badMethod { int

I have an array of objects on which I would like to perform block operations. I am not sure the best way to do this. I am doing something like in the code below but I don't think this is the best practice. What is the best way to do such an operation? - (void)performBlockOnAllObjects:(NSArray*)objects completion:(void(^)(BOOL success))completionHandler { NSInteger counter = objects.count; for (MyObject *obj in objects) { [obj performTaskWithCompletion:^(NSError *error) { counter--; if (counter == 0) { completionHandler(YES); } }]; } } Typically you'd use dispatch groups for this. You "enter"