objective-c-blocks

I've started using Objective-C blocks today. I wrote the following code: NSArray *array = @[@25, @"abc", @7.2]; void (^print)(NSUInteger index) = ^(NSUInteger index) { NSLog(@"%@", array[index]); }; for (int n = 0; n < 3; n++) print(n); Which works properly. I needed to change the array variable after its declaration, though, so I tried using the following code: NSArray *array; void (^print)(NSUInteger index) = ^(NSUInteger index) { NSLog(@"%@", array[index]); }; array = @[@25, @"abc", @7.2]; for (int n = 0; n < 3; n++) print(n); However, that doesn't work. The console just prints (null) three

In my project, I have both Objective-C and Swift code. I have some objects that have properties containing blocks to clean up some UITableView configuration. Using it works in Objective-C, but crashes when using Swift. I have reduced the problem to be as minimal as possible, while still being reproducible. // in Objective-C @interface MyClass : NSObject @property (copy, nonatomic) NSString* (^block)(); - (NSString *)callTheBlock; @end @implementation MyClass - (NSString *)callTheBlock { if (self.block) { return self.block(); } else { return @"There is no spoon"; } } @end // In Swift // I

I have a function which takes a block as parameter: typedef void (^ MyBlock)(int); -(void)doTask:(MyBlock)theBlock{ ... } I need to run above function on another thread, I want to use - performSelector:onThread:withObject:waitUntilDone: , my current code: NSThread *workerThread = [[NSThread alloc] init]; [workerThread start]; [self performSelector:@selector(doTask:) onThread:workerThread withObject:??? waitUntilDone:NO]; BUT, How can I pass MyBlock parameter with this approach? (Please don't suggest GCD, I am wondering how can I do with my current code, is it possible?) This answer assumes you

I have written a simple test case that follows Apple's documentation and I am not seeing the results that I'm expecting. Here's the code: - (void)testExample2 { NSLog(@"1"); dispatch_semaphore_t semaphore = dispatch_semaphore_create(0); dispatch_async(dispatch_get_main_queue(), ^{ NSLog(@"3"); dispatch_semaphore_signal(semaphore); }); NSLog(@"2"); dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER); NSLog(@"4"); dispatch_release(semaphore); } I would expect to read: 1, 2, 3, 4 but instead my console just shows me 1, 3. I've been able to work around the issue using DISPATCH_TIME_NOW in a