IOS学习 GCD 基础 串行/并行/主线程、同步/异步

@implementation ViewController

- (void)viewDidLoad {

[superviewDidLoad];

// Do any additional setup after loading the view, typically from a nib.

}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent
*)event{

[selfdemo];

}

//GCD 基础

-(void)demo{

/* //用block语法写

void(^mytask)(void) = ^{};

//创建任务

dispatch_block_t task = ^{

NSLog(@"%@",[NSThread currentThread]);

};

//获取队列

dispatch_queue_t queue = dispatch_get_global_queue(0, 0);

//把任务放入队列中

dispatch_async(queue, task);

//简单写法 工作中常用代码

dispatch_async(dispatch_get_global_queue(0, 0), ^{

NSLog(@"NSThread %@",[NSThread currentThread]);

});

*/

//多个任务

for (int i =0; i <20;
i++) {

dispatch_async(dispatch_get_global_queue(0,0),
^{

[NSThreadsleepForTimeInterval:3];

NSLog(@"NSThread %@ %d",[NSThreadcurrentThread],i);

});

}

}

//串行队列 同步执行

//不开线程，在当前线程下执行

//任务是有序执行的

-(void)demo1{

//创建队列 参数1：队列名称
参数2：队列属性

dispatch_queue_t serialqueue =dispatch_queue_create("serialqueue",DISPATCH_QUEUE_SERIAL);

for (int i =0; i <20;
i++) {

dispatch_sync(serialqueue, ^{

NSLog(@"%@ %d",[NSThreadcurrentThread],i);

});

}

}

//串行队列 异步执行

//开一个线程

//任务是有序执行的

-(void)demo2{

dispatch_queue_t serialqueue =dispatch_queue_create("serialqueue",DISPATCH_QUEUE_SERIAL);

for (int i =0; i <20;
i++) {

dispatch_async(serialqueue, ^{

NSLog(@"%@ %d",[NSThreadcurrentThread],i);

});

}

}

//并行队列 异步执行（效率最大化）

//开多个线程

//任务是无序执行的

-(void)demo3{

dispatch_queue_t concurrentQueue =dispatch_queue_create("concurrentQueue",DISPATCH_QUEUE_CONCURRENT);

for (int i =0; i <20;
i++) {

dispatch_async(concurrentQueue, ^{

NSLog(@"%@ %d",[NSThreadcurrentThread],i);

});

}

}

//并行队列 同步执行 (并行无效，按同步执行)与串行同步一样

//不开线程，在当前线程下执行

//任务是有序执行的

-(void)demo4{

dispatch_queue_t concurrentQueue =dispatch_queue_create("concurrentQueue",DISPATCH_QUEUE_CONCURRENT);

for (int i =0; i <20;
i++) {

dispatch_sync(concurrentQueue, ^{

NSLog(@"%@ %d",[NSThreadcurrentThread],i);

});

}

}

//主队列异步执行

//不开线程，在主线程下执行

//任务是有序执行的

-(void)demo5{

//获取主线程

dispatch_queue_t mainqueue =dispatch_get_main_queue();

for (int i =0; i <
20; i++) {

dispatch_async(mainqueue, ^{

NSLog(@"main queue %@ %d",[NSThreadcurrentThread],i);

});

}

}

//主队列同步执行

//死锁:在主线程下,往主线程里添加同步任务

//解决办法:1,将主线程改子线程 2,同步改为异步

-(void)demo6{

//获取主线程

dispatch_queue_t mainqueue =dispatch_get_main_queue();

dispatch_sync(mainqueue, ^{

NSLog(@"main queue %@",[NSThreadcurrentThread]);

});

}