iphone - 调用 dismissViewControllerAnimated 时的 exc_bad_access

Question

我有一个向上滑动的 ViewController。当您单击“保存”时，它会向服务器发送请求。请求完成后，它会关闭 ViewController。我将 NSURLConnection 切换为使用异步和 block (https://github.com/rickerbh/NSURLConnection-Blocks)。现在关闭 ViewController 会抛出“线程 2:程序收到信号:EXC_BAD_ACCESS”。如果重要的话，我正在使用 ARC。

- (IBAction) savePressed
{
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"http://api.com/items/create"]];

    //NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    [NSURLConnection asyncRequest:request success:^(NSData *data, NSURLResponse *response) {
        [self close];
    } failure:^(NSData *data, NSError *error) {
        [self close];
    }];
}

- (void) close
{
    [self dismissViewControllerAnimated:YES completion:nil];
}

这是日志

2012-10-24 10:32:43.780 Prayrbox[22268:1703] bool _WebTryThreadLock(bool), 0x1f21fd90: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now...
1   0x347dc927 WebThreadLock
2   0x36718615 <redacted>
3   0x366d0a85 <redacted>
4   0x3678d789 <redacted>
5   0x366c0637 <redacted>
6   0x366d50e7 <redacted>
7   0x368c1f11 <redacted>
8   0x366d4969 <redacted>
9   0x36744745 <redacted>
10  0x366907ad <redacted>
11  0x7ef71 -[ComposeViewController close]
12  0x7eec5 __36-[ComposeViewController savePressed]_block_invoke_0
13  0x82d8f __56+[NSURLConnection(Blocks) asyncRequest:success:failure:]_block_invoke_0
14  0x37e8811f <redacted>
15  0x37e96259 <redacted>
16  0x37e963b9 <redacted>
17  0x37b30a11 <redacted>
18  0x37b308a4 start_wqthread
[Switching to process 10755 thread 0x2a03]
[Switching to process 10755 thread 0x2a03]
[unknown](gdb) 

我已经花了 2 个小时来寻求这方面的帮助。如果有人知道什么可以帮助，请说出来! :)

Answer 1

乍一看，我同意上面的评论，即在关闭 View 时您可能走错了线程。

UI 的东西应该在 Main 上完成，所以要强制执行，你可以这样做:

-(void) close {
    if([NSThread isMainThread]) {
        [self dismissViewControllerAnimated:YES completion:nil];
    }
    else {
        [self performSelectorOnMainThread:@selector(close)
                               withObject:nil
                           waitUntilDone:YES];
    }
}

而不是从你的 block 中执行 performSelectorOnMainThread，这将确保无论何时调用它，你都会在主线程上。