iphone - ios @try @catch 在从@catch 返回时阻止 EXC_BAD_ACCESS

Question

我的 viewDidLoad 中的这个 @try-@catch block 在返回时因 EXC_BAD_ACCESS 而崩溃；在 catch 中执行并且警报不显示:

    @try
    {        
        errorText = @"thumbnails_array";

        unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
        // Customize unarchiver here
        self.thumbnails_array = [unarchiver decodeObjectForKey:@"thumbnails_array"];
        [unarchiver finishDecoding];
        [unarchiver release];


        errorText = @"ThumbNailViewController";

        archivePath = [app.phojoArchiveDir stringByAppendingPathComponent:@"ThumbNailViewController.archive"];
        data = [NSData dataWithContentsOfFile:archivePath];
        unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
        // Customize unarchiver here
        [unarchiver decodeObjectForKey:@"self"];
        [unarchiver finishDecoding];
        [unarchiver release];

        errorText = @"assetsGroupURL";

        archivePath = [app.phojoArchiveDir stringByAppendingPathComponent:@"assetsGroupURL.archive"];
        data = [NSData dataWithContentsOfFile:archivePath];
        unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
        // Customize unarchiver here
        app.assetsGroupURL = [unarchiver decodeObjectForKey:@"assetsGroupURL"];
        [unarchiver finishDecoding];
        [unarchiver release];


    }
    @catch (NSException *exception) 
    {
       UIAlertView * alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Phojo is unable to restore the previous editing session." delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil];
        [alert show];
        [alert release];

        NSLog(@"Exception %@ thrown while unarchving %@: Reason: %@ Items in userInfo = %d Stack Trace: %@", [exception name], errorText, [exception reason], [[exception userInfo] count], [NSThread callStackSymbols]);  
        [self.thumbnails_array   release];
        self.thumbnails_array = nil;
        [app.assetsGroupURL release];
        app.assetsGroupURL = nil;

        return;


    }

此代码在 viewDidLoad 中运行，以检索在上一次应用程序运行期间存档的数据。我在这段代码中遇到了一个异常，指出存档是不可理解的。但是随着它崩溃，根本没有办法让应用程序运行，因为它在启动时和捕获时都崩溃了。有什么想法吗？

Answer 1

您的 assetsGroupURL 或 thumbnails_array 属性(或两者)被声明为 retain。这很好，但这意味着当您同时调用 [self.theProperty release] 和 self.theProperty = nil 时，您正在释放 theProperty两次:第二次调用是使用 retain 生成的 setter 并在其当前值上隐式调用 release。删除 release 调用，您应该不会再看到 EXC_BAD_ACCESS。