objective-c - 寻找有关如何调试 "message sent to deallocated instance"的指针

Question

我收到以下错误:

* -[URLViewController respondsToSelector:]: message sent to deallocated instance 0xdb5c3b0

我很困惑如何开始调试它。有人可以给我一些关于从哪里开始看的指示吗？

如果你想看，这里有一些代码。这实际上是一个 URL 拦截器，因此每个链接都在 presentModalViewController 中打开

- (BOOL)openURL:(NSURL *)url{
    URLViewController * web = [[URLViewController alloc] init];
    web.url = url;
    UINavigationController * nav = [[UINavigationController alloc] initWithRootViewController:web];
    [nav.navigationBar setTintColor:[UIColor blackColor]];
    [nav setModalPresentationStyle:UIModalPresentationFormSheet];
    [self.detailViewController presentModalViewController:nav animated:NO];
    [web release];
    [nav release];
    return YES;
}

如果对 URLViewController 实现感兴趣，请看这里:

@implementation URLViewController
@synthesize webview;
@synthesize url;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (IBAction) done:(id) sender
{
    [self dismissModalViewControllerAnimated:YES];   
}

- (IBAction) openInSafari:(id) sender
{
   [(CVore*)[CVore sharedApplication] openURL:url withOverride:NO];
}

- (void)dealloc
{
    [super dealloc];
}

- (void)didReceiveMemoryWarning
{
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.webview.delegate = self;
     NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];
    [webview loadRequest:requestObj];
    [self.navigationItem setRightBarButtonItem:[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(done:)]]; 
     [self.navigationItem setLeftBarButtonItem:[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAction target:self action:@selector(openInSafari:)]]; 
    // Do any additional setup after loading the view from its nib.
}

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    NSString* title = [webView stringByEvaluatingJavaScriptFromString: @"document.title"];
    self.title = title;
    //self.navigationItem.title = title;
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return YES;
}

@end

更新:跟踪这个之后，我认为我的错误是我需要在 [super dealloc] 之前将 UIWebView 委托(delegate)设置为 nil 这是正确的吗？当我这样做时，它不再崩溃

Answer 1

您已经很快发布了您的 URLViewController 实例，或者您没有保留它。还要检查您在哪里使用了 = 而不是使用合成的 setter(可能会创建一个僵尸)，如果有的话。如果不查看任何代码，就很难提供帮助。

__

当 URLViewController 被释放和释放时，你的 webview 在你调用 super 时真的应该也是，因为它是一个类成员。但是，对象不能保留它们的代表(以防止“保留循环”)，所以如果你想知道如何在你的 webview 上添加额外的保留，在这里或其他地方，它的代表仍然可能最终为 nil 并导致崩溃.例如，您是否有用于 webview 的 retain 合成器？你有没有调用这个？