1.串行队列
1.1串行队列创建
dispatch_queue_t queue = dispatch_queue_create("lanou", DISPATCH_QUEUE_SERIAL);
1.2串行队列的同步执行(不开启多线程)
for (int i = 0 ; i < 10; i ++) {
dispatch_sync(queue, ^{
NSLog(@"线程为%@ - %d",[NSThread currentThread],i);
});
}
1.3串行队列的异步执行 (开启多线程 但最多只能开启一条)
for (int i = 0 ; i < 10; i ++) {
dispatch_async(queue, ^{
NSLog(@"线程为%@ - %d",[NSThread currentThread],i);
});
}
NSLog(@"come here%@",[NSThread currentThread]);
2.并发队列
2.1并发队列创建
dispatch_queue_t queue = dispatch_queue_create("lanou", DISPATCH_QUEUE_CONCURRENT);
2.2并发队列的同步执行 （不会开启多线程 ）
for (int i = 0 ; i < 10; i ++) {
dispatch_sync(queue, ^{
NSLog(@"线程为%@ - %d",[NSThread currentThread],i);
});
}
NSLog(@"come here%@",[NSThread currentThread]);
2.3并发队列的异步执行 （开启多线程，但编译器不会控制线程的数量，数量由底层线程池决定，开启过多的线程可能会影响系统内存）
for (int i = 0 ; i < 10; i ++) {
dispatch_async(queue, ^{
NSLog(@"线程为%@ - %d",[NSThread currentThread],i);
});
}
NSLog(@"come here%@",[NSThread currentThread]);
3.主队列
3.1主队列的创建
dispatch_queue_t queue = dispatch_get_main_queue();
3.2主队列的同步执行 (主队列的同步执行会造成主队列和主线程的的互锁 如下面的代码)
for (int i = 0 ; i < 10; i ++) {
dispatch_sync(queue, ^{
NSLog(@"线程为%@ - %d",[NSThread currentThread],i);
});
}
NSLog(@"come here%@",[NSThread currentThread]);
改善方法 （将其写成block 用并发队列异步执行）
void (^myBlock)() = ^{
for (int i = 0 ; i < 10; i ++) {
dispatch_sync(queue, ^{
NSLog(@"线程为%@ - %d",[NSThread currentThread],i);
});
}
NSLog(@"come here%@",[NSThread currentThread]);
};
dispatch_async(dispatch_queue_create("lanou", DISPATCH_QUEUE_CONCURRENT), myBlock);
3.3主队列的异步执行（不会开启多线程）
for (int i = 0 ; i < 10; i ++) {
dispatch_async(queue, ^{
NSLog(@"线程为%@ - %d",[NSThread currentThread],i);
});
}
NSLog(@"come here%@",[NSThread currentThread]);
4.全局队列
4.1性质
1.全局队列和并发队列的特性基本一致
2.并发队列 MRC 必须使用dispatch_release进行释放，而全局队列不用
3.ARC 都不用进行释放
4.如果需要使用阻塞的话，必须使用并发队列，下面会进行介绍(第三方框架的话 最好使用并发队列)
5.全局队列更方便
4.2全局队列的创建
dispatch_queue_t queue = dispatch_get_global_queue(0, 0);
4.3全局队列的同步执行（与并发队列一样 不会开启多线程）
for (int i = 0 ; i < 10; i ++) {
dispatch_sync(dispatch_get_global_queue(0, 0), ^{
NSLog(@"线程为%@ - %d",[NSThread currentThread],i);
});
}
NSLog(@"come here%@",[NSThread currentThread]);
4.4全局队列的异步执行 （与并发队列一样 会开启多线程）
for (int i = 0 ; i < 10; i ++) {
dispatch_async(dispatch_get_global_queue(0, 0), ^{
NSLog(@"线程为%@ - %d",[NSThread currentThread],i);
});
}
NSLog(@"come here%@",[NSThread currentThread]);
5.并发队列同步异步的简单套用使用
dispatch_queue_t queue = dispatch_queue_create("bing", DISPATCH_QUEUE_CONCURRENT);
void (^task)() = ^{
dispatch_sync(queue, ^{
NSLog(@"login %@",[NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"Download a %@",[NSThread currentThread]);
NSLog(@"Download b %@",[NSThread currentThread]);
NSLog(@"Download c %@",[NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"Download d %@",[NSThread currentThread]);
NSLog(@"Download e %@",[NSThread currentThread]);
NSLog(@"Download f %@",[NSThread currentThread]);
});
};
dispatch_async(dispatch_get_global_queue(0, 0), task);
6.阻塞异步(如下面代码 对添加队列进行阻塞，使照片全部下载完毕后 进行添加)
dispatch_queue_t queue = dispatch_queue_create("lanou", DISPATCH_QUEUE_CONCURRENT);
dispatch_async(queue, ^{
//模拟延时
[NSThread sleepForTimeInterval:1.0];
//模拟网络加载
NSString *fileName = [NSString stringWithFormat:@"%02ld.jpg",index + 1];
NSString *path = [[NSBundle mainBundle]pathForResource:fileName ofType:nil];
UIImage *image = [UIImage imageWithContentsOfFile:path];
//一定要使用自定义的并发队列 如果使用全局队列 无法阻塞队列
dispatch_barrier_async(queue, ^{
NSLog(@"添加图片%ld %@",index,[NSThread currentThread]);
//将图像添加到数组
[self.pictureList addObject:image];
});
NSLog(@"下载完成%@ %@",fileName,[NSThread currentThread]);
});
7.一次性执行（一般使用在单例的创建中 dispatch_once 是线程安全的 提示 dispatch_once 内部也是有一把锁 性能很高 苹果推荐）
+(instancetype)shareDiseaseData{
static <#类名#> *handler = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
if (!handler) {
handler = [[<#类名#> alloc]init];
}
});
return handler;
}
8.调度组 （创建调度组 将异步任务加载到调度组中，当所有任务完成的时候，调度组可以接受到通知）
8.1调度组的创建
dispatch_group_t group = dispatch_group_create();
8.2调度组的使用
dispatch_group_async(group, _queue, ^{
[NSThread sleepForTimeInterval:1];
NSLog(@"download a %@",[NSThread currentThread]);
});
dispatch_group_async(group, _queue, ^{
[NSThread sleepForTimeInterval:3];
NSLog(@"download b %@",[NSThread currentThread]);
});
dispatch_group_async(group, _queue, ^{
NSLog(@"download c %@",[NSThread currentThread]);
});
8.3调度组通知
dispatch_group_notify(group, _queue, ^{
NSLog(@"全部下载完了 %@",[NSThread currentThread]);
});
