糟糕的 UIViewController

发布于 2024-11-26 11:31:55 字数 1003 浏览 1 评论 0原文

我有一个 viewController 给我带来了问题...

UIViewController *nextController = [[NextView alloc] initWithNibName:@"NextView" bundle:nil];
[currentPageController.view removeFromSuperview];
[self.view addSubview:nextController.view];

我的应用程序因 EXC_BAD_ACCESS 崩溃。

有人知道什么可能会导致这种情况吗？

提前致谢！

更新

使用断点并逐步执行代码后，问题似乎出在我的 viewController 的 viewDidLoad 中的这段代码：

NSString *noteToSet;

        if ([Settings isData]) {
            noteToSet = [NSString stringWithFormat:@"Data, "];
        }
        if ([Settings isGeom]) {
            if ([noteToSet isEqualToString:@""]) {
                noteToSet = [NSString stringWithFormat:@"Geom, "];
            } else {
                noteToSet = [noteToSet stringByAppendingFormat:@"Geom, "];
            }
        }

有人看到那里有问题吗？非常感谢！

已修复

通过使用空白值@""初始化字符串来修复它

noteToSet = [NSString stringWithFormat:@""];

原文

I have ONE viewController that is giving me a problem...

UIViewController *nextController = [[NextView alloc] initWithNibName:@"NextView" bundle:nil];
[currentPageController.view removeFromSuperview];
[self.view addSubview:nextController.view];

My app crashes here with an EXC_BAD_ACCESS.

Does anybody have ANY idea what could cause this?

Thanks in advance!

UPDATE

After using Breakpoints and stepping through the code, the problem seems to be with this bit of code in the viewDidLoad of my viewController:

NSString *noteToSet;

        if ([Settings isData]) {
            noteToSet = [NSString stringWithFormat:@"Data, "];
        }
        if ([Settings isGeom]) {
            if ([noteToSet isEqualToString:@""]) {
                noteToSet = [NSString stringWithFormat:@"Geom, "];
            } else {
                noteToSet = [noteToSet stringByAppendingFormat:@"Geom, "];
            }
        }

Anybody see a problem there?
Thanks so much!

FIXED

Fixed it by initializing the string with the blank value @""

noteToSet = [NSString stringWithFormat:@""];

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夜无邪 2024-12-03 11:31:55

所以答案的第一部分是 - 如果你的 viewController 无法加载并且你不知道为什么 - 检查 viewDidLoad 中的代码，这就是我的问题所在，它让我疯狂地试图找出 viewController 本身的问题当它实际上是 viewDidLoad 中的 NSString 问题时。

第二部分是，您不能使用 [stringName isEqualToString:@""] 将 NSString 与空白值进行比较，除非您从 NSUSerDefaults 获取该字符串，或者除非您首先将该字符串设置为等于 @""。

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信愁 2024-12-03 11:31:55

我在发布的代码中没有看到任何会导致异常的内容。但是，您发布的两段代码都包含以下行：

currentPageController = nextController;
[currentPageController retain];
[nextController release];

由于第一行使 currentPageController 指向与 nextController 相同的对象，因此第二行和第三行相互抵消。你不妨这样写：

currentPageController = nextController;

就这样吧。代码中其他地方的类似误解很容易导致您过于频繁地错过保留或释放，并导致您似乎看到的那种错误指针。

I don't see anything in the posted code that'd cause the exception. However, both pieces of code that you posted contain the lines:

currentPageController = nextController;
[currentPageController retain];
[nextController release];

Since the first line makes currentPageController point to the same object as nextController, the second and third lines cancel each other out. You might as well write:

currentPageController = nextController;

and leave it at that. A similar misunderstanding at some other point in the code could easily cause you to miss a retain or release once too often and cause the sort of bad pointer that you seem to be seeing.

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