在目标C中执行selectoronmainthread的最佳方法? [英] Best way to performselectoronmainthread in objective c?

问题描述

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.从设备访问在线数据库时，需要在单独的线程上执行此操作，以免冻结UI/主线程.但是，当响应从数据库中获取的数据时，我在主线程上调用此方法:performSelectorOnMainThread.事实是，这只允许我向方法(WithObject)发送一个参数/对象，有时我想传递更多的参数.另一件事是我必须传递这个对象.如果我崩溃了，我无法通过nil.

I'm writing a client-server app to iPhone. And I have a question about threading. When I access my online database from the device, I need to do this on a separate thread to not freeze the UI/main thread. But when responding to the data I've fetched from the database I call this method on the main thread: performSelectorOnMainThread. The thing is that this only lets me send one argument/object to the method (WithObject), sometimes I have more arguments I want to pass. and another thing about it is that I HAVE TO pass this one object. I can't pass nil, if I do the app crashes.

这是我今天的代码..我担心我使用的是方法并以错误的方式进行线程化.

This is my code today.. and I'm worried that I'm using the methods and threading the wrong way.

- (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];
}

这是这样做的好方法吗，除了performSelectorOnMainThread之外，您还能指出其他更好的方法吗?

Is this a good way of doing this, is there anything besides performSelectorOnMainThread this you can point me to, that works better?

如您所见，在此示例中，我将nil传递给NSString参数，因为我必须传递一些东西，如果我在方法中没有NSString作为arg，则传递nil时应用程序将崩溃.这个?..请让我更清楚一点！

As you can see I pass nil to an NSString argument in this example, because I HAVE to pass something, if I don't have NSString as an arg in the method, the app crashes evan when passing nil.. Why is this?.. please make this a bit clearer for me!

//谢谢！

推荐答案

好，您已经在使用dispatch_async.然后，您应该使用

Well, you're already using dispatch_async. Then you should just use

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

从后台线程内部在主线程上执行操作.例如

from inside your background thread to perform things on the main thread. For example,

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

它对您调用的方法的参数数量没有任何限制.

It doesn't have any constraint on the number of arguments for the methods you call.

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