objective-c – 在目标c中执行选择器主线程的最佳方法？

我正在为iPhone编写客户端 – 服务器应用程序.我有一个关于线程的问题.当我从设备访问我的在线数据库时,我需要在单独的线程上执行此操作以不冻结UI /主线程.但是当响应我从数据库中获取的数据时,我在主线程上调用此方法：performSelectorOnMainThread.问题是,这只能让我向方法(WithObject)发送一个参数/对象,有时候我想传递更多的参数.关于它的另一件事是我必须通过这一个对象.如果我发现应用程序崩溃,我无法通过nil.

这是我今天的代码..我担心我正在使用这些方法并以错误的方式进行操作.

- (IBAction)testServerAction:(id)sender {

    [self.imageView setHidden:YES];
    [self.activityView setHidden:NO];
    [self.activityView startAnimating];
    dispatch_queue_t testServer = dispatch_queue_create("Test-Server-Thread",NULL);
    dispatch_async(testServer,^{

        if ([self.arrayWithServerConnections count] > 0)
        {
            NSString *messageToShow;
            if ([self testServerMethod])
            {
                messageToShow = @"Server is working!";
                [self performSelectorOnMainThread:@selector(showMessageBoxWithString:) withObject:messageToShow waitUntilDone:YES];
                [self performSelectorOnMainThread:@selector(threadedUIActivityRemover:) withObject:nil waitUntilDone:YES];
            }else
            {
                messageToShow = @"Server is NOT working!";
                [self performSelectorOnMainThread:@selector(showMessageBoxWithString:) withObject:messageToShow waitUntilDone:YES];
                [self performSelectorOnMainThread:@selector(threadedUIActivityRemover:) withObject:nil waitUntilDone:YES];
            }
        }

    });

    dispatch_release(testServer);
}

-(void)threadedUIActivityRemover:(NSString *)string
{
    [self.imageView setHidden:NO];
    [self.activityView setHidden:YES];
    [self.activityView stopAnimating];
}

这是一个很好的方法吗,除了performSelectorOnMainThread之外还有什么可以指向我的,那效果更好吗？

正如你所看到的,在这个例子中我将nil传递给NSString参数,因为我必须传递一些东西,如果我没有NSString作为方法中的arg,应用程序在传递nil时崩溃了evan ..为什么会这样？请让我对此更清楚一点！

//谢谢！

dispatch_async(dispatch_get_main_queue(),^ { ... } );

if ([self testServerMethod])
        {
            dispatch_async(dispatch_get_main_queue(),^ {
               [self showMessageBoxWithString: @"Server is working!"];
               [self threadedUIActivityRemover:nil];
            } );
        }else ...