objective-c-blocks

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

问题 I created an APIController in my application that has several methods that call specific api urls and return a model object populated with the result of the api call. The api works with json and up to now my code looks like the following: //Definition: - (MyModel *)callXYZ; - (MyModel *)callABC; - (MyModel *)call123; //Implementation of one: - (MyModel *)callXYZ { //Build url and call with [NSData dataWithContentsOfURL: url]; //Create model and assign data returned by api return model; } Now

问题 I have using blocks and ARC, and found in some situation, iOS only crash in Release build. It was wrong way to write code, like this. -(IBAction)clickedButtonA:(UIBarButtonItem*)sender event:(UIEvent*)event { NSMutableArray *arrRows = [NSMutableArray arrayWithCapacity:0]; #warning this code only crash on Release Build.... Don't use this NSMutableDictionary * dicRow = [NSMutableDictionary dictionaryWithCapacity:0]; [arrRows addObject:dicRow]; dispatch_block_t block = ^{ NSString *str =

问题 I'm trying to move lengthy OpenGL draw operations into a GCD queue so I can get other stuff done while the GPU grinds along. I would much rather prefer to do this with GCD vs. adding real threading to my app. Literally all I want to do is be able to Not block on a glDrawArrays() call so the rest of the UI can stay responsive when GL rendering gets very slow. Drop glDrawArrays() calls when we aren't finishing them anyway (don't build up a queue of frames that just grows and grows) On Apple's

问题 I need to test for the availability of blocks at runtime, so I can handle backwards compatibility with iOS 3. Any tips? edit: So far I'm doing if (!NSClassFromString(@"NSBlockOperation")) {...} Seems to be working... 回答1: You will also need to make sure to weak link the libSystem.B.dylib , set your base SDK to 4.0 and deployment target to 3.1.3, as described here. A good overview on how to deal with iOS versioning issues can also be found in this this Cocoa with Love article: Tips & Tricks

问题 I have a read-only property isFinished in my interface file: typedef void (^MyFinishedBlock)(BOOL success, NSError *e); @interface TMSyncBase : NSObject { BOOL isFinished_; } @property (nonatomic, readonly) BOOL isFinished; and I want to set it to YES in a block at some point later, without creating a retain cycle to self : - (void)doSomethingWithFinishedBlock:(MyFinishedBlock)theFinishedBlock { __weak MyClass *weakSelf = self; MyFinishedBlock finishedBlockWrapper = ^(BOOL success, NSError *e

问题 Sup guys, I'm trying to do a function that calls itself but by putting everything on one block, As you can see, the following function is intended to be called an indefinite amount of times (until arcrandom returns a number lower than 50) and you should expect as an output a variable number of "RUNNING" messages, depending on chance. void (^_test_closure)(void) = ^ { NSLog(@"RUNNING"); if(arc4random() % 100 > 50) { _test_closure(); } }; _test_closure(); However, when running it, I get an EXC

问题 How do I write the following: typedef void (^T)(void); T f() { return ^{}; } without the typedef? 回答1: void (^f())(void) { return ^{}; } You'd better keep the typedef as the return type is not easy to understand in this form. 来源： https://stackoverflow.com/questions/3948173/objective-c-block-type-as-return-value

问题 How do I write the following: typedef void (^T)(void); T f() { return ^{}; } without the typedef? 回答1: void (^f())(void) { return ^{}; } You'd better keep the typedef as the return type is not easy to understand in this form. 来源： https://stackoverflow.com/questions/3948173/objective-c-block-type-as-return-value

问题 If I want to pass nothing for an Objective-C block, what keyword should I use, NULL or nil ? I'm asking this because an Objective-C block is an Objective-C object (as I know), but represented as a function pointer. NULL and nil both indicate a 0x0 pointer, however they are different semantically. So I'm concerned about this. 回答1: Blocks are not represented as function pointers. They're represented as blocks, and this is denoted by the ^ symbol in their declaration. Down under the hood, the