运行 addToFavourites 函数时的 EXC_BAD_ACCESS

Question

我有一个 addToFavourites 函数，它导致 EXC_BAD_ACCESS 错误。 基本上，我有收藏夹视图控制器，其中包含用户之前添加的所有收藏夹的列表，现在当单击其中一个收藏夹时，它会将视图推送到详细视图控制器，这工作正常。在详细视图控制器上，我有一个“添加到收藏夹”按钮，如果检测到该键已存在于 addToFavourites 字典中，则该按钮将更改为从收藏夹中删除。当用户从收藏夹页面以及列出所有detailViews的主页访问此detailViewController时，就会出现问题。他们能够做到这一点，因为我有一个标签栏。

所以说我在通过收藏夹页面访问的详细视图中，收藏夹按钮有“从收藏夹中删除”，这是正确的。但如果我单击“从收藏夹中删除”按钮，该按钮会更改为“添加到收藏夹”并将其从字典中删除。到目前为止一切正常。现在，当我切换到相同的详细视图，但这次从选项卡栏上的不同选项卡访问时，首先收藏夹按钮仍然显示“从收藏夹中删除”，当我第一次单击此按钮时，它会更改为“添加到收藏夹”，然后当我再次单击它时，出现 EXC_BAD_ACCESS 错误。

这是 addToFavouritesFunction：

- (IBAction)addToFavourites:(id)sender {
    NSString *type = [[NSUserDefaults standardUserDefaults]objectForKey:@"type"];
    if(type == @"v") {
        NSString *area = [[NSUserDefaults standardUserDefaults]objectForKey:@"area"];
        NSString *ID1 = [[NSUserDefaults standardUserDefaults]objectForKey:@"ID1"];
        if([[addToFavouritesDictionary allKeys] containsObject:ID1]) {
            NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
            NSString *documentsDirectory = [paths objectAtIndex:0];
            NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"/SavedDict.data"];
            [addToFavouritesDictionary removeObjectForKey:ID1];
            [favouritesButton setTitle:@"+ Favourites" forState:(UIControlState)UIControlStateNormal];
            [addToFavouritesDictionary writeToFile:filePath atomically: YES];
            NSLog(@"New Dictionary: %@", addToFavouritesDictionary);
        } else {
            NSString *ID1 = [[NSUserDefaults standardUserDefaults]objectForKey:@"ID1"];
            [addToFavouritesDictionary setObject:Name forKey:ID1];
            [favouritesButton setTitle:@"- Favourites" forState:(UIControlState)UIControlStateNormal];
            NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
            NSString *documentsDirectory = [paths objectAtIndex:0];
            NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"/SavedDict.data"];
            [addToFavouritesDictionary writeToFile:filePath atomically: YES];
            NSLog(@"Mutable Dictionary: %@", addToFavouritesDictionary);
            //[addToFavouritesDictionary release];
        }
} else {
        //NSString *area = [[NSUserDefaults standardUserDefaults]objectForKey:@"area"]; 
        NSString *ID2 = [[NSUserDefaults standardUserDefaults]objectForKey:@"ID2"];
        if([[addToFavouritesDictionary allKeys] containsObject:ID2]) {
            NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
            NSString *documentsDirectory = [paths objectAtIndex:0];
            NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"/SavedDict.data"];
            [addToFavouritesDictionary removeObjectForKey:ID2];
            [favouritesButton setTitle:@"+ Favourites" forState:(UIControlState)UIControlStateNormal];
            [addToFavouritesDictionary writeToFile:filePath atomically: YES];
            NSLog(@"Dictionary: %@", addToFavouritesDictionary);
        } else {
            NSString *ID2 = [[NSUserDefaults standardUserDefaults]objectForKey:@"ID2"];
            [addToFavouritesDictionary setObject:Name forKey:ID2];
            [favouritesButton setTitle:@"- Favourites" forState:(UIControlState)UIControlStateNormal];
            NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
            NSString *documentsDirectory = [paths objectAtIndex:0];
            NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"/SavedDict.data"];
            [addToFavouritesDictionary writeToFile:filePath atomically: YES];
            NSLog(@"Mutable Dictionary: %@", addToFavouritesDictionary);
        }
    }
}

感谢您的帮助！

Answer 1

使用调试器检查它是否准确地显示崩溃行...然后设置断点以检查值

Answer 2

嗯...您的 addToFavouritesDictionary 对象或您的 Name 对象已被释放。您如何创建这些对象？要么你提前释放了它们，要么你一开始就没有保留它们。

Objective-C 内存管理

Answer 3

您可能不应该使用以下行：

if(type == @"v") {

您在这里所做的是将变量 type 的指针与字符串 @"v" 的指针进行比较。相反，您应该使用比较字符串的内容的方法：

if ([type isEqualToString:@"v") {

编辑

保持标题相同的最简单方法是将文本存储在 NSUserDefaults 中。每当按下按钮时，您都可以执行如下操作：

// For "Add to Favorites"
[[NSUserDefaults standardUserDefaults] setObject:@"+ Favorites" forKey:@"ButtonState"];

// For "Remove from Favorites"
[[NSUserDefaults standardUserDefaults] setObject:@"- Favorites" forKey:@"ButtonState"];

然后，当视图加载时，您将执行如下操作：

[favoritesButton setTitle:(NSString*)[[NSUserDefaults standardUserDefaults] objectForKey:@"ButtonState"] forState:UIControlStateNormal];