objective-c-blocks

I have some code that downloads an image and assigns it within a block. The code currently works however I want to refactor it into a separate method, however after the refactoring I get a compilation error. This is the original code which compiles and runs with the downloaded image being assigned successfully: - (void) someMethod { … MyObject* object = [[MyObject alloc] init]; [self.objects addObject: object]; NSString* graphRequest = [NSString stringWithFormat:@"%@%@%@", @"https://graph.facebook.com/", fbid, @"/picture?type=square"]; FBRequest *fbRequest = [FBRequest requestForGraphPath:

Mike Ash created an example of using blocks to handle callbacks from sheets, which seems very nice. This was in turn updated to work with garbage collection by user Enchilada in another SO question at beginSheet: block alternative? , see below. @implementation NSApplication (SheetAdditions) - (void)beginSheet:(NSWindow *)sheet modalForWindow:(NSWindow *)docWindow didEndBlock:(void (^)(NSInteger returnCode))block { [self beginSheet:sheet modalForWindow:docWindow modalDelegate:self didEndSelector:@selector(my_blockSheetDidEnd:returnCode:contextInfo:) contextInfo:Block_copy(block)]; } - (void)my

I'm working on some CoreAnimation stuff. A navigation controller with a few view controllers. And the view controllers have UISCrollViews for different "pages" of a "brochure." On each page, there might be some animation that gets triggered when the user flips to that page. I was trying something like this (for one-shot animations). void (^animationBlock)() = ^{ static bool alreadyTriggered = NO; if(alreadyTriggered) return; [CATransaction begin]; [CATransaction setCompletionBlock: ^{ alreadyTriggered = YES; }]; // Do me some animations... [CATransaction commit]; }; NSMutableDictionary*

Ever since their introduction in iOS 4, I have been wondering about the internal implementation of the UIView 's block-based animation methods. In particular I would like to understand what mystical features of Objective C are used there to capture all the relevant layer state changes before and after execution of the animation block. Observing the black-box implementation, I gather that it needs to capture the before-state of all layer properties modified in the animation block, to create all the relevant CAAnimations . I guess it does not do a snapshot of whole view hierarchy, as that would

I'm trying to implement a very simple strategy class in Objective-C that allows for strategies to be defined inline instead of being defined through inheritance. Currently my code looks like this: @interface SSTaskStrategy : NSObject { (NSArray *)(^strategy)(void); } @end I thought this would work, but I'm getting the error Expected specifier-qualifier-list before '(' token Any ideas how to make this work? You should drop the parentheses around NSArray * in your ivar definition: @interface SSTaskStrategy : NSObject { NSArray * (^strategy)(void); } @end Also, I highly recommend that you use a

The following code crashes, since the contents of sentence go away when the final block exits. #import <Foundation/Foundation.h> int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; // simple block test - just iterate over some items and // add them to a string NSArray *items = [NSArray arrayWithObjects:@"why ", @"must ", @"this ",nil]; __block NSString *sentence = @""; [items enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { sentence = [sentence stringByAppendingFormat:@"%@",obj]; }]; // crash! NSLog(@"Sentence is %@"

For example, in GKScore 's reportScoreWithCompletionHandler ( documentation ), suppose you call [score reportScoreWithCompletionHandler:^(NSError *error) { // do some stuff that may be thread-unsafe }]; In which thread will the completion handler be called: the main thread, the same thread as reportScoreWithCompletionHandler was called, or a different thread (presumably the thread that the actual score reporting is done)? In other words, does the work done in the completion handler need to be thread-safe (as in, it doesn't matter what thread it's done in)? mlaster In practical terms it doesn't