iOS learning notes

the difference of segue style

dispatch_async() 调用以后立即返回，dispatch_sync() 调用以后等到block执行完以后才返回，dispatch_sync()会阻塞当前线程。 

http://www.linuxidc.com/Linux/2011-10/45821.htm

通知机制：

http://www.cnblogs.com/pengyingh/articles/2367374.html

NSDictionary

+ (id)JSONObjectWithData:(NSData *)data options:(NSJSONReadingOptions)opt error:(NSError **)error

解析json的过程

问题：http://www.cocoachina.com/bbs/read.php?tid=110907