/**

• 线程组

*/

-(void)group
{
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_group_t group = dispatch_group_create();
    //1、下载图片1
    dispatch_group_async(group, queue, ^{
        //图片路径
        NSURL *url = [NSURL URLWithString:@""];
        //加载图片
        NSData *data = [NSData dataWithContentsOfURL:url];
        //生成图片
        self.image1 = [UIImage imageWithData:data];
    });

//2、下载图片2

    dispatch_group_async(group, queue, ^{
        //图片路径
        NSURL *url = [NSURL URLWithString:@""];
        //加载图片
        NSData *data = [NSData dataWithContentsOfURL:url];
        //生成图片
        self.image2 = [UIImage imageWithData:data];
    });
    
    dispatch_group_notify(group, queue, ^{
        //开启图形上下文
        UIGraphicsBeginImageContext(CGSizeMake(100, 100));
        //绘制图片
        [self.image1 drawInRect:CGRectMake(0, 0, 50, 100)];
        [self.image2 drawInRect:CGRectMake(50, 0, 50, 100)];
        //取得上下文中的图片
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
        // 结束上下文
        UIGraphicsEndImageContext();
        
        // 回到主线程 显示图片
        dispatch_async(dispatch_get_main_queue(), ^{
            self.imageView.image = image;
        });
        
    });
}

/**

• GCD的文件剪切
  */

-(void)GCDMoveFile
{
    NSString *from = @"";
    NSString *to = @"";
    NSFileManager *mgr = [NSFileManager defaultManager];
    NSArray *subPaths = [mgr subpathsAtPath:from];
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_apply(subPaths.count, queue, ^(size_t index) {
        NSString *subPath = subPaths[index];
        NSString *fromFullPath = [from stringByAppendingPathComponent:subPath];
        NSString *toFullPath = [to stringByAppendingPathComponent:subPath];
        //剪切
        [mgr moveItemAtPath:fromFullPath toPath:toFullPath error:nil];
    });
}

/**

• 传统的文件剪切
  */

-(void)moveFile
{
    NSString *from = @"";
    NSString *to = @"";
    NSFileManager *mgr = [NSFileManager defaultManager];
    NSArray *subPaths = [mgr subpathsAtPath:from];
    for (NSString *subPath in subPaths) {
        NSString *fromFullPath = [from stringByAppendingPathComponent:subPath];
        NSString *toFullPath = [to stringByAppendingPathComponent:subPath];
        //剪切
        [mgr moveItemAtPath:fromFullPath toPath:toFullPath error:nil];
    }
}

-(void)GCD
{
    
      //全局
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        //回到主线，刷新UI
        dispatch_async(dispatch_get_main_queue(), ^{
            
            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
                
                dispatch_async(dispatch_get_main_queue(), ^{
                    
                });
            });
            
        });
    });

#pragma  mark  一次性代码
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        NSLog(@" ---------run");
        //整个程序只执行一次（线程是安全的）
    });
    ```

//快速遍历，快速迭代
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_apply(10, queue, ^(size_t index) {
    NSLog(@"%zd --- %@",index,[NSThread currentThread].name);
});

pragma mark ---- 栅栏函数

//创建一个并发队列

// label "相当于队列的名字"
dispatch_queue_t queue1 = dispatch_queue_create("NEME.D", DISPATCH_QUEUE_CONCURRENT);
dispatch_barrier_async(queue1, ^{
//在前面的任务执行结束后它才执行，而且它后面的任务等它执行完成之后 才会执行

//    这个queue不能是全局的并发队列；
});

pragma mark -- 延迟执行 --

// GCD延迟函数
dispatch_after(dispatch_time( DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)),dispatch_get_main_queue(), ^{
    
});

//调用NSObject的方法
[self performSelector:@selector(run) withObject:nil afterDelay:2.0];
// 使用NSTmer
[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(run) userInfo:nil repeats:NO];

}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
//开启子线程
[self performSelectorInBackground:@selector(downLoad) withObject:nil];
}

-(void)downLoad
{
NSURL *url = [NSURL URLWithString:@""];
NSData *data = [NSData dataWithContentsOfURL:url];
UIImage *image = [UIImage imageWithData:data];
//回到主线程 ，展示图片
[self.imageView performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:NO];
//方法2
// [self.imageView performSelector:@selector(setImage:) onThread:[NSThread mainThread] withObject:image waitUntilDone:NO];
}