标签：void color inter control queue sel import span elf
代码1 - 未使用信号量控制并发：
#import "ViewController.h" @interface ViewController () @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ for (NSUInteger i = 0; i < 10; ++i) { NSLog(@"Task - 1"); } }); dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ for (NSUInteger i = 0; i < 10; ++i) { NSLog(@"Task - 2"); } }); } @end
输出：
Task - 1 Task - 2 Task - 1 Task - 2 Task - 1 Task - 2 Task - 1 Task - 2 Task - 1 Task - 2 Task - 1 Task - 2 Task - 1 Task - 2 Task - 1 Task - 2 Task - 1 Task - 2 Task - 1 Task - 2
代码 - 使用信号量控制并发：
#import "ViewController.h" @interface ViewController () @property (nonatomic, strong) dispatch_semaphore_t semaphore; @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; self.semaphore = dispatch_semaphore_create(1); dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ dispatch_semaphore_wait(self.semaphore, DISPATCH_TIME_FOREVER); for (NSUInteger i = 0; i < 10; ++i) { NSLog(@"Task - 1"); } dispatch_semaphore_signal(self.semaphore); }); dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ dispatch_semaphore_wait(self.semaphore, DISPATCH_TIME_FOREVER); for (NSUInteger i = 0; i < 10; ++i) { NSLog(@"Task - 2"); } dispatch_semaphore_signal(self.semaphore); }); } @end
输出：
Task - 1 Task - 1 Task - 1 Task - 1 Task - 1 Task - 1 Task - 1 Task - 1 Task - 1 Task - 1 Task - 2 Task - 2 Task - 2 Task - 2 Task - 2 Task - 2 Task - 2 Task - 2 Task - 2 Task - 2
标签：void color inter control queue sel import span elf
原文地址：http://www.cnblogs.com/xwoder/p/7460783.html
