iOS GCD不同场景的使用比较
/**
* async -- 并发队列
* 会创建线程，一般同时开多条
* 并发执行任务
*/
<span style="font-size:14px;">- (void)asyncGlobalQueue
{
// 获得全局的并发队列
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
// 将 任务 添加 全局队列 中去 异步 执行
dispatch_async(queue, ^{
NSLog(@"-----下载图片1---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片2---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片3---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片4---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片5---%@", [NSThread currentThread]);
});
}
</span>
<span style="font-size:14px;">-----下载图片4---<NSThread: 0x7fbd52c9b390>{number = 5, name = (null)}
-----下载图片3---<NSThread: 0x7fbd52f00230>{number = 4, name = (null)}
-----下载图片2---<NSThread: 0x7fbd52e3eed0>{number = 3, name = (null)}
-----下载图片5---<NSThread: 0x7fbd52e2eb40>{number = 6, name = (null)}
-----下载图片1---<NSThread: 0x7fbd52c06010>{number = 2, name = (null)}</span>
/**
* async -- 串行队列
* 会创建线程, 一般只开1条线程
* 串行执行任务（一个任务执行完毕后再执行下一个任务）
*/
- (void)asyncSerialQueue
{
// 1.创建一个串行队列
dispatch_queue_t queue = dispatch_queue_create("cn.heima.queue", NULL);
// 2.将任务添加到串行队列中 异步 执行
dispatch_async(queue, ^{
NSLog(@"-----下载图片1---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片2---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片3---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片4---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片5---%@", [NSThread currentThread]);
});
}
-----下载图片1---<NSThread: 0x7fd4c5b00b50>{number = 2, name = (null)}
-----下载图片2---<NSThread: 0x7fd4c5b00b50>{number = 2, name = (null)}
-----下载图片3---<NSThread: 0x7fd4c5b00b50>{number = 2, name = (null)}
-----下载图片4---<NSThread: 0x7fd4c5b00b50>{number = 2, name = (null)}
-----下载图片5---<NSThread: 0x7fd4c5b00b50>{number = 2, name = (null)}
/**
* async -- 主队列
*/
- (void)asyncMainQueue
{
// 1.主队列(添加到主队列中的任务，都会自动放到主线程中去执行)
dispatch_queue_t queue = dispatch_get_main_queue();
// 2.添加 任务 到主队列中 异步 执行
dispatch_async(queue, ^{
NSLog(@"-----下载图片1---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片2---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片3---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片4---%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"-----下载图片5---%@", [NSThread currentThread]);
});
}
-----下载图片1---<NSThread: 0x7faaca905000>{number = 1, name = main}
-----下载图片2---<NSThread: 0x7faaca905000>{number = 1, name = main}
-----下载图片3---<NSThread: 0x7faaca905000>{number = 1, name = main}
-----下载图片4---<NSThread: 0x7faaca905000>{number = 1, name = main}
-----下载图片5---<NSThread: 0x7faaca905000>{number = 1, name = main}
/**
* sync -- 主队列(会卡死)
*/
- (void)syncMainQueue
{
NSLog(@"syncMainQueue----begin--");
// 1.主队列(添加到主队列中的任务，都会自动放到主线程中去执行)
dispatch_queue_t queue = dispatch_get_main_queue();
// 2.添加 任务 到主队列中 异步 执行
dispatch_sync(queue, ^{
NSLog(@"-----下载图片1---%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"-----下载图片2---%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"-----下载图片3---%@", [NSThread currentThread]);
});
NSLog(@"syncMainQueue----end--");
}
syncMainQueue----begin--
/**
* sync -- 并发队列
* 不会创建线程
* 串行执行任务（一个任务执行完毕后再执行下一个任务）
* 并发队列失去了并发的功能
*/
- (void)syncGlobalQueue
{
// 获得全局的并发队列
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
// 将 任务 添加到 全局并发队列 中 同步 执行
dispatch_sync(queue, ^{
NSLog(@"-----下载图片1---%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"-----下载图片2---%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"-----下载图片3---%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"-----下载图片4---%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"-----下载图片5---%@", [NSThread currentThread]);
});
}
-----下载图片1---<NSThread: 0x7fe5b2904c30>{number = 1, name = main}
-----下载图片2---<NSThread: 0x7fe5b2904c30>{number = 1, name = main}
-----下载图片3---<NSThread: 0x7fe5b2904c30>{number = 1, name = main}
-----下载图片4---<NSThread: 0x7fe5b2904c30>{number = 1, name = main}
-----下载图片5---<NSThread: 0x7fe5b2904c30>{number = 1, name = main}
/**
* sync -- 串行队列
* 不会创建线程
* 串行执行任务（一个任务执行完毕后再执行下一个任务）
*/
- (void)syncSerialQueue
{
// 创建一个串行队列
dispatch_queue_t queue = dispatch_queue_create("cn.heima.queue", NULL);
// 将 任务 添加到 串行队列 中 同步 执行
dispatch_sync(queue, ^{
NSLog(@"-----下载图片1---%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"-----下载图片2---%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"-----下载图片3---%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"-----下载图片4---%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"-----下载图片5---%@", [NSThread currentThread]);
});
}
-----下载图片1---<NSThread: 0x7fdb40f05020>{number = 1, name = main}
-----下载图片2---<NSThread: 0x7fdb40f05020>{number = 1, name = main}
-----下载图片3---<NSThread: 0x7fdb40f05020>{number = 1, name = main}
-----下载图片4---<NSThread: 0x7fdb40f05020>{number = 1, name = main}
-----下载图片5---<NSThread: 0x7fdb40f05020>{number = 1, name = main}