objective-c-blocks

问题 Looking at this page: http://www.mikeash.com/pyblog/friday-qa-2010-12-31-c-macro-tips-and-tricks.html I found this snippet of code with ^{ ... }() syntax, what are the caret/brackets doing? #define MAX(x, y) (^{ \ int my_localx = (x); \ int my_localy = (y); \ return my_localx > my_localy ? (my_localx) : (my_localy); \ }()) It looks like its creating an anonymous function or something. What is this concept called? Where can I read about it? 回答1: It's a C block. It's quite like an anonymous

问题 Looking at this page: http://www.mikeash.com/pyblog/friday-qa-2010-12-31-c-macro-tips-and-tricks.html I found this snippet of code with ^{ ... }() syntax, what are the caret/brackets doing? #define MAX(x, y) (^{ \ int my_localx = (x); \ int my_localy = (y); \ return my_localx > my_localy ? (my_localx) : (my_localy); \ }()) It looks like its creating an anonymous function or something. What is this concept called? Where can I read about it? 回答1: It's a C block. It's quite like an anonymous

问题 I have a question regarding the best practice for declaring a block as a variable . Initially I wrote my block variable like this: id actionHandler = ^(UIAlertAction * action) { // Handling code }; To be later used like so: UIAlertAction *action = [UIAlertAction actionWithTitle:@"Title" style:UIAlertActionStyleDefault handler:actionHandler]; But when I came across Apple's Working With Blocks guide, I saw I could rewrite it like so: void (^actionHandler)(UIAlertAction * action) = ^

问题 While reading through the blocks conceptual overview in Apple Docs, I saw the following statement: Although blocks are available to pure C and C++, a block is also always an Objective-C object. How is this possible? I mean an Objective-C object available in pure C. I'm getting confused. 回答1: How is this possible? I mean an Objective-C object available in pure C. Matt Gallagher wrote an article that nicely explains how blocks work. In a nutshell, blocks are defined as structs that meet the

问题 While reading through the blocks conceptual overview in Apple Docs, I saw the following statement: Although blocks are available to pure C and C++, a block is also always an Objective-C object. How is this possible? I mean an Objective-C object available in pure C. I'm getting confused. 回答1: How is this possible? I mean an Objective-C object available in pure C. Matt Gallagher wrote an article that nicely explains how blocks work. In a nutshell, blocks are defined as structs that meet the

问题 This question already has answers here : Fix warning “Capturing [an object] strongly in this block is likely to lead to a retain cycle” in ARC-enabled code (7 answers) Closed 5 years ago . I create the custom cell with the activity indicator view With using the SDWebImage I hidden the activity indicator when the image is downloaded [customCell.userPhotoImageView setImageWithURL:[NSURL URLWithString:[[thisNotify user]imageURL]] placeholderImage:nil completed:^ (UIImage *image, NSError *error,

问题 I'm using Xcode 4.3.3 and developing for iOS 5.0+. In development of an ARC iOS application, I've started using blocks as a callback mechanism for asynchronous operations. The app works fine in the simulator and on the device. Then I ran it the profiler for the first time, and it started crashing on me nearly right away - in particular, an EXC_BAD_ACCESS when trying to invoke the first callback block. After a little investigation, it was clear the difference in behavior was because the

问题 So I'm storing block actions into a nsmutabledictionary and then recalling them when a response comes back on a websocket. This turns async request into a block syntax. Here's the stripped down code: - (void)sendMessage:(NSString*)message responseAction:(void (^)(id))responseAction { NSString *correlationID = (NSString*)[[message JSONValue] objectForKey:@"correlationId"]; [self.messageBlocks setObject:responseAction forKey:correlationID]; NSLog(@"Sending message: %@", correlationID);

问题 So I'm storing block actions into a nsmutabledictionary and then recalling them when a response comes back on a websocket. This turns async request into a block syntax. Here's the stripped down code: - (void)sendMessage:(NSString*)message responseAction:(void (^)(id))responseAction { NSString *correlationID = (NSString*)[[message JSONValue] objectForKey:@"correlationId"]; [self.messageBlocks setObject:responseAction forKey:correlationID]; NSLog(@"Sending message: %@", correlationID);

问题 Writing a program that demonstrate different sorting algorithm in C++ on Mac. I found two quicksort implementation, qsort and qsort_b. The first one is of course the old-fashioned, seen-everywhere qsort. But there's qsort_b, which takes an block rather than a function. Here's my code: #include <cstdlib> #include <cstdio> #include <iostream> #include <cstdio> #include <ctime> #define DATA 1000000 using namespace std; int compare(const void* a, const void* b) { return *(int*)a - *(int*)b; } int