objective-c-blocks - w3toppers.com

Blocks instead of performSelector:withObject:afterDelay: [duplicate]

There’s no built-in way to do that, but it’s not too bad to add via a category: @implementation NSObject (PerformBlockAfterDelay) – (void)performBlock:(void (^)(void))block afterDelay:(NSTimeInterval)delay { block = [[block copy] autorelease]; [self performSelector:@selector(fireBlockAfterDelay:) withObject:block afterDelay:delay]; } – (void)fireBlockAfterDelay:(void (^)(void))block { block(); } @end Credit to Mike Ash for the basic implementation.

Using weak self in dispatch_async function

Assuming, self is an object pointer to a UIViewController. Things to consider: A UIViewController is a “UIKit” object. UIKit objects shall not be sent methods on non-main threads, that is – those methods must execute on the main thread only! A block that has been enqueued in a queue – whether this was synchronously or … Read more

Creating delegates on the spot with blocks

Okay, I finally got around to putting WoolDelegate up on GitHub. Now it should only take me another month to write a proper README (although I guess this is a good start). The delegate class itself is pretty straightforward. It simply maintains a dictionary mapping SELs to Block. When an instance recieves a message to … Read more

How can I retrieve a return value from a completion block?

You’re missing some basics about asynchronous development with blocks. You can’t have a dispatched block return from anywhere but its own scope. Think of each block as its own method, instead of inline code. I think what you’re looking for is something similar to this… – (void)testWithHandler:(void(^)(int result))handler { [obj somemethodwithcompeltionblock:^{ int someInt = 10; … Read more

How to use “enumerateChildNodesWithName” with Swift in SpriteKit?

For now, don’t trust autocomplete to insert the code you need — it drops in signatures from the “header”, but a block signature is not the same as the declaration you need when inserting your own closure for a block parameter. The formal way to write a closure would be to replicate the signature inside … Read more

UIButton block equivalent to addTarget:action:forControlEvents: method?

I just implemented this. It work’s like a charm! And it wasn’t even hard. typedef void (^ActionBlock)(); @interface UIBlockButton : UIButton { ActionBlock _actionBlock; } -(void) handleControlEvent:(UIControlEvents)event withBlock:(ActionBlock) action; @end @implementation UIBlockButton -(void) handleControlEvent:(UIControlEvents)event withBlock:(ActionBlock) action { _actionBlock = action; [self addTarget:self action:@selector(callActionBlock:) forControlEvents:event]; } -(void) callActionBlock:(id)sender{ _actionBlock(); } @end

How to simplify callback logic with a Block?

It sounds like you wish to communicate with an existing class which is designed to take a delegate object. There are a number of approaches, including: using a category to add block-based variants of the appropriate methods; use a derived class to add the block-based variants; and write a class which implements the protocol and … Read more

How to dispatch on main queue synchronously without a deadlock?

I need to use something like this fairly regularly within my Mac and iOS applications, so I use the following helper function (originally described in this answer): void runOnMainQueueWithoutDeadlocking(void (^block)(void)) { if ([NSThread isMainThread]) { block(); } else { dispatch_sync(dispatch_get_main_queue(), block); } } which you call via runOnMainQueueWithoutDeadlocking(^{ //Do stuff }); This is pretty much … Read more

Alternatives to dispatch_get_current_queue() for completion blocks in iOS 6?

The pattern of “run on whatever queue the caller was on” is appealing, but ultimately not a great idea. That queue could be a low priority queue, the main queue, or some other queue with odd properties. My favorite approach to this is to say “the completion block runs on an implementation defined queue with … Read more

Why can’t we use a dispatch_sync on the current queue?

dispatch_sync does two things: queue a block blocks the current thread until the block has finished running Given that the main thread is a serial queue (which means it uses only one thread), if you run the following statement on the main queue: dispatch_sync(dispatch_get_main_queue(), ^(){/*…*/}); the following events will happen: dispatch_sync queues the block in … Read more