Question

我有一个UITabBarController。其中一个选项卡显示应用程序“书签”，这些书签是保存到Core Data（SQLLite）数据库的基本搜索类型。

当我加载我的应用程序时，转到书签视图（bookmarksViewController），它会在我的appDelegate（getBookmarks）中加载一个函数，并在表格中显示结果。这种方法很完美，可以在视图之间切换，在其他视图中执行preform搜索切换回来。没问题。它每次都加载内容。但是......当我加载搜索视图并添加新书签，然后切换回书签视图时，它会以错误消息“EXC_BAD_ACCESS”消失。我不知道为什么以及如何解决这个问题。

这是我的代码：
的 bookmarksViewController.m

[...]
- (void)viewDidLoad {
    [super viewDidLoad];

 theBookmarks = nil;

    // Set up the edit and add buttons.
    self.navigationItem.rightBarButtonItem = self.editButtonItem;

 [self setTitle:NSLocalizedString(@"Bookmarks", @"bookmarksViewController")];
}

- (void)viewWillAppear:(BOOL)animated { 
 if (theBookmarks != nil)
 {
  NSLog(@"Release it!");
  [theBookmarks release];
 }

 NSLog(@"Appear 1");

 stationenAppDelegate *stationen = (stationenAppDelegate *)[[UIApplication sharedApplication]delegate];

 NSLog(@"Appear 1 - stage 2");

 theBookmarks = [[stationen getBookmarks] retain];

 NSLog(@"Appear 2");

    [super viewWillAppear:animated];
}
[...]

myAppDelegate.m

[...]
/**
 * Bookmarks
 *
 * Type definition
 * 1: Station search
 * 2: Train search
 * 3: Interuption search
 */

- (NSMutableArray*)getBookmarks
{
 NSLog(@"check 1");

 NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];

 NSEntityDescription *entity = [NSEntityDescription entityForName:@"bookmarks" 
             inManagedObjectContext:self.managedObjectContext];
 [fetchRequest setEntity:entity];

 NSLog(@"check 2");

 NSError *error;
 NSArray *items = [[self.managedObjectContext
        executeFetchRequest:fetchRequest error:&error] retain];
 NSMutableArray *returnArray = [[[NSMutableArray alloc] initWithArray:items] retain];

 NSLog(@"check 4");

 [fetchRequest release];

 return returnArray;
}

- (void)addBookmark:(bookmarks_object*)theBookmark
{
 BOOL exists = [self checkIfBookmarkExistsUsingBookmark:theBookmark];

 if(!exists)
 {
  bookmarks *saveBookmark = (bookmarks *)[NSEntityDescription insertNewObjectForEntityForName:@"bookmarks"
                    inManagedObjectContext:self.managedObjectContext];

  [saveBookmark setStation_from:theBookmark.station_from];
  [saveBookmark setStation_to:theBookmark.station_to];
  [saveBookmark setAddDate:[[NSDate alloc] init]];
  [saveBookmark setSort:theBookmark.sort];
  [saveBookmark setPlace:[[NSNumber alloc] initWithInt:([[self getBookmarks] count]+1)]];
  [saveBookmark setName:([theBookmark.type isEqualToString:@"1"] || [theBookmark.type isEqualToString:@"2"] ? theBookmark.station_from : [[NSString alloc] initWithFormat:@"%@ -> %@", theBookmark.station_from, theBookmark.station_to])];
  [saveBookmark setType:theBookmark.type];

  [self saveAction];
  [saveBookmark release];
 }
 else {
  NSLog(@"No need to add, %@ already exists!", theBookmark.station_from);
 }
}

- (BOOL)checkIfBookmarkExistsUsingBookmark:(bookmarks_object*)theBookmark
{
 // Get the categories
 NSArray *historyArray = [self getBookmarks];

 BOOL exists = NO;

 for(bookmarks *dbHistory in historyArray)
 {
  if ([theBookmark.type isEqualToString:@"1"] || [theBookmark.type isEqualToString:@"2"])
  {
   if([[dbHistory station_from] isEqualToString:theBookmark.station_from])
   {
    exists = YES;
    continue;
   }
  }
  else if ([theBookmark.type isEqualToString:@"3"])
  {
   if([[dbHistory station_from] isEqualToString:theBookmark.station_from] && 
      [[dbHistory station_to] isEqualToString:theBookmark.station_to])
   {
    exists = YES;
    continue;
   }
  }
  else {
   NSLog(@"Error! Unknown type!");
   return NO;
  }
 }

 return exists;
}
[...]

堆栈跟踪（流程：打开应用，加载书签视图，切换到搜索视图，添加书签，切换回来）

2010-09-19 13:51:54.554 stationen[7256:207] Appear 1
2010-09-19 13:51:54.555 stationen[7256:207] Appear 1 - stage 2
2010-09-19 13:51:54.555 stationen[7256:207] check 1
2010-09-19 13:51:54.560 stationen[7256:207] check 2
2010-09-19 13:51:54.562 stationen[7256:207] check 4
2010-09-19 13:51:54.562 stationen[7256:207] Appear 2
2010-09-19 13:52:26.669 stationen[7256:207] check 1
2010-09-19 13:52:26.670 stationen[7256:207] check 2
2010-09-19 13:52:26.671 stationen[7256:207] check 4
2010-09-19 13:52:26.671 stationen[7256:207] No need to add, 230 already exists!
2010-09-19 13:52:30.509 stationen[7256:207] Release it!
2010-09-19 13:52:30.510 stationen[7256:207] Appear 1
2010-09-19 13:52:30.510 stationen[7256:207] Appear 1 - stage 2
Program received signal:  “EXC_BAD_ACCESS”.

Answer 1

您是否尝试使用调试器查看错误的位置？
在Xcode中打开调试器，然后使用Breakpoints构建应用程序。在模拟器中执行所有步骤以重现错误当您发现错误时，调试器会在应用程序崩溃之前停止应用程序，您将看到在调试器视图中实现了方法...其中一个或多个将以黑色突出显示/写入。在这些方法中存在错误。单击该方法，您将看到错误的位置，然后您将能够修改该代码以解决错误...

希望这可以帮到你！：）

Answer 2

问题是appDelegate在分配和使用它之间以某种方式释放。我为它添加了一个保留并在之后释放它。

按Mark建议使用NSZombieEnabled找到它。谢谢！

奇怪的EXC_BAD_ACCESS，我做错了什么？

2 个答案: