一段异步操作的代码（清理缓存）

dispatch_async(
dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
, ^{
                    NSString *cachPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];
                    
                    NSArray *files = [[NSFileManager defaultManager] subpathsAtPath:cachPath];
                    NSLog(@"files :%d",[files count]);
                    for (NSString *p in files) {
                        NSError *error;
                        NSString *path = [cachPath stringByAppendingPathComponent:p];
                        if ([[NSFileManager defaultManager] fileExistsAtPath:path]) {
                            [[NSFileManager defaultManager] removeItemAtPath:path error:&error];
                        }
                    }
                    [self performSelectorOnMainThread:@selector(clearCacheSuccess) withObject:nil waitUntilDone:YES];});

-(void)clearCacheSuccess
{
    NSLog(@"清理成功");
}