objective-c-blocks

问题 If the code inside a block calls a method, will a retain cycle exist if that method references self? In other words, does all code downstream of a block need to use the weakSelf/strongSelf pattern? For example: __weak __typeof__(self) weakSelf = self; Myblock block = ^{ [weakSelf doSomething]; }; . . . - (void)doSomething { self.myProperty = 5; // Is this ok or does it need to use a weakSelf? } 回答1: Retain cycle will be triggered only if you retain self inside the block. Otherwise it will

问题 I have a method call (it's a call from AFNetworking): AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) { NSLog(@"IP Address: %@", [JSON valueForKeyPath:@"origin"]); } failure:^(NSURLRequest *request , NSURLResponse *response , NSError *error , id JSON) { NSLog(@"Failed: %@",[error localizedDescription]); }]; and I'm trying to pull the sucess and failure blocks out into a

问题 I wrote a class for declaratively describing a sequence of UIView animations. My method takes a vararg of animation blocks and puts them in an array. So in my loop I want to do this: [animations addObject:[[block copy] autorelease]]; I first copy the block so that it is moved to the heap, allowing it to be retain 'ed by the array. Then I autorelease it to relinquish ownership (because the array retains it). However this crashes when the animations array is dealloc'd. (My understanding is that

问题 I have a method which returns a block. I want to add a breakpoint inside the block. In Xcode adding a breakpoint on a line that's inside the block causes execution to pause when the method is returned and not when the block is executed. How do I add a breakpoint inside a block? 回答1: I had the same difficulty, until I tried using Xcode 4's LLDB debugger (go to Product>Edit Scheme to turn it on). Perhaps you'll have better luck with it. 回答2: From the documentation You can set breakpoints and

问题 I have a method which returns a block. I want to add a breakpoint inside the block. In Xcode adding a breakpoint on a line that's inside the block causes execution to pause when the method is returned and not when the block is executed. How do I add a breakpoint inside a block? 回答1: I had the same difficulty, until I tried using Xcode 4's LLDB debugger (go to Product>Edit Scheme to turn it on). Perhaps you'll have better luck with it. 回答2: From the documentation You can set breakpoints and

问题 I'm trying to define a block that takes a block as an argument. What's wrong with the following line of code? id (^cacheResult)(NSString *, id(^)(void)) = ^(NSString *name, id(^)(void)block) { NSObject *item = nil; block(); return item; }; Why does the compiler keep giving errors like Parameter name omitted and Expected ")" ? 回答1: id (^cacheResult)(NSString *, id(^)(void)) = ^(NSString *name, id(^block)(void)) { NSObject *item = nil; block(); return item; }; Blocks have similar syntax to

问题 I'm trying to define a block that takes a block as an argument. What's wrong with the following line of code? id (^cacheResult)(NSString *, id(^)(void)) = ^(NSString *name, id(^)(void)block) { NSObject *item = nil; block(); return item; }; Why does the compiler keep giving errors like Parameter name omitted and Expected ")" ? 回答1: id (^cacheResult)(NSString *, id(^)(void)) = ^(NSString *name, id(^block)(void)) { NSObject *item = nil; block(); return item; }; Blocks have similar syntax to

问题 I've looked at the methods for block based animation and noticed there is no equivalent parameter or option for [UIView setAnimationRepeatCount:] . What's the simplest way to repeat an animation a fixed number of times? Do you, for instance, chain them using the completion block? 回答1: Set a completion callback - re-initiate the animation in it - and keep track of the counter yourself. 回答2: I just asked a similar question and then I read the 2010-11-15 release of the View Programming Guide for

问题 I am trying to create a method that will return me a ALAsset for a given asset url. (I need upload the asset later and want to do it outside the result block with the result.) + (ALAsset*) assetForPhoto:(Photo*)photo { ALAssetsLibrary* library = [[[ALAssetsLibrary alloc] init] autorelease]; __block ALAsset* assetToReturn = nil; NSURL* url = [NSURL URLWithString:photo.assetUrl]; NSLog(@"assetForPhoto: %@[", url); [library assetForURL:url resultBlock:^(ALAsset *asset) { NSLog(@"asset: %@",

问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: Caret in objective C What does this ^ syntax mean in Objective-C? I am tired by searching the meaning of symbol ^ in Objective C. I have seen it in lot of projects especially in back ground running tasks. I will put a link http://developer.apple.com/library/ios/#samplecode/StitchedStreamPlayer/Introduction/Intro.html#//apple_ref/doc/uid/DTS40010092 and in MyStreamingMovieViewController.m you can find the