xcode “EXC_BAD_ACCESS”，“-[CFString 保留]：在表格中滚动时发送到释放实例的消息”

"EXC_BAD_ACCESS", "-[CFString retain]: message sent to deallocated instance" when scrolling in a table

提问by Taz

APPLICATION DESCRIPTION: I am a new iPhone developer. I am working on an application which used two table views then a detail view. The first level table view presents a few categories, when a category is selected a list of topics related to that category is displayed. When a topic is selected a detail view is presented related to that topic.

应用程序描述：我是一名新的 iPhone 开发人员。我正在开发一个应用程序，该应用程序使用两个表视图和一个详细信息视图。The first level table view presents a few categories, when a category is selected a list of topics related to that category is displayed. 选择主题后，将显示与该主题相关的详细信息视图。

When I run the app in the simulator everything seems to work fine (but only briefly!):

当我在模拟器中运行应用程序时，一切似乎都正常（但只是短暂的！）：

• First Level Table View:this view with the categories loads fine and works without any problems.
• Topic List View:This view also appears to work fine, but only briefly. It loads all of the correct topics, and I can even quickly scroll up and down through the entire list of topics - but this only works for a couple of seconds while scrolling (after which the application crashes). I can also select any of the topics and the detail view loads successfully.
• Detail View:works fine, no problems.

• 第一级表视图：带有类别的此视图可以正常加载并且可以正常工作。
• 主题列表视图：此视图似乎也工作正常，但只是短暂的。它加载了所有正确的主题，我什至可以在整个主题列表中快速上下滚动 - 但这仅在滚动时工作几秒钟（之后应用程序崩溃）。我还可以选择任何主题并成功加载详细信息视图。
• 详细视图：工作正常，没有问题。

I am using two nibs for the application: MainWindow.xib displays the First Level and Topic View tables. A TopicDetail.xib is used to display the detail information for a topic.

我为应用程序使用了两个笔尖：MainWindow.xib 显示第一级和主题视图表。TopicDetail.xib 用于显示主题的详细信息。

DATA:The First Level View gets its data from a plist which consists of an array of strings. The Topic List View gets its data from a plist of dictionaries. Each dictionary consists of five strings. One of these strings contains "Tags" of categories which relate to the topic. When a category from the First Level View is selected, the Topic View selects the topics with "Tags" which match the selected category, and displays them on the Topic View Table.

数据：第一级视图从由字符串数组组成的 plist 中获取数据。主题列表视图从字典 plist 中获取其数据。每个字典由五个字符串组成。这些字符串之一包含与主题相关的类别的“标签”。当从第一级视图中选择一个类别时，主题视图选择具有与所选类别匹配的“标签”的主题，并将它们显示在主题视图表上。

PROBLEM:My problem is with the second "Topic View." A couple of ways in which I have been able to cause the crash:

问题：我的问题是第二个“主题视图”。我能够导致崩溃的几种方式：

• If I quickly scroll up and down through the topic list, for a couple of seconds everything works normally, then the application crashes.

• If I scroll one cell off of the screen, I can scroll the same cell back onto the screen without a problem. If I repeat this (scroll the same cell off of the screen a second time then try to scroll it back onto the screen), the app crashes when scrolling the cell back onto the screen.

• 如果我在主题列表中快速上下滚动，几秒钟后一切正常，然后应用程序崩溃。

• 如果我从屏幕上滚动一个单元格，我可以毫无问题地将同一个单元格滚动回屏幕。如果我重复此操作（再次将同一单元格从屏幕上滚动，然后尝试将其滚动回屏幕），则在将单元格滚动回屏幕时应用程序会崩溃。

ERROR MESSAGES:The initial error message that was returned was EXC_BAD_ACCESS. When I enabled NSZombieEnabled I got the error message "-[CFString retain]: message sent to deallocated instance"

错误消息：返回的初始错误消息是EXC_BAD_ACCESS。当我启用 NSZombieEnabled 时，我收到错误消息“ -[CFString retain]: message sent to deallocated instance”

Based on these error messages and my research, I believe I have a memory allocation problem where "retain" is being called on an object that has been released, but I can't figure out where this occuring and how to resolve it! Any help would be greatly appreciated - thank you in advance!!

根据这些错误消息和我的研究，我相信我有一个内存分配问题，其中在已释放的对象上调用了“retain”，但我无法弄清楚发生这种情况的位置以及如何解决它！任何帮助将不胜感激 - 在此先感谢您！！

CODE:

代码：

First Level View Controller.h:

一级视图 Controller.h：

#import 
@class TopicListController;

@interface FirstLevelViewController : UITableViewController {
    NSArray *controllers;
    TopicListController *childController;
}
@property (nonatomic, retain) NSArray *controllers;
@end

First Level View Controller.m:

一级视图 Controller.m：

#import "FirstLevelViewController.h"
#import "TopicListController.h"
#import "TopicAppDelegate.h"

@implementation FirstLevelViewController
@synthesize controllers;

- (void)viewDidLoad
{
    self.title = @"Categories"; 
    NSString *path = [[NSBundle mainBundle] pathForResource:@"TopicCategoryList" ofType:@"plist"];  
    NSMutableArray *array = [[NSMutableArray alloc] initWithContentsOfFile:path];   
    self.controllers = array;
    [array release];
    [super viewDidLoad];
}

- (void)viewDidUnload
{
    self.controllers = nil;
    [childController release];
    childController = nil;
    [super viewDidUnload];
}

- (void) dealloc
{
    [controllers release];
    [childController release];
    [super dealloc];
}

#pragma mark -
#pragma mark Table Data Source Methods

- (NSInteger)tableView:(UITableView *)tableview numberOfRowsInSection:(NSInteger)section
{
    return [self.controllers count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *FirstLevelCell = @"FirstLevelCell";    
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:FirstLevelCell];

    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:FirstLevelCell] autorelease];
    }
    NSUInteger row = [indexPath row];
    cell.textLabel.text = [controllers objectAtIndex:row];
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
    return cell;
}

#pragma mark -
#pragma mark Table View Delegate Methods

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (childController == nil) {
        childController = [[TopicListController alloc] init];
    }

    childController.title = @"Topics";
    NSUInteger row = [indexPath row];

    NSString *selectedCategory = [self.controllers objectAtIndex:row];
    childController.selectedCategory = selectedCategory;
    [self.navigationController pushViewController:childController animated:YES];
}                            

@end

Topic List Controller.h:

主题列表 Controller.h：

#import 
@class TopicDetailController;

@interface TopicListController : UITableViewController {

    NSArray *list;
    NSString *selectedCategory;
    TopicDetailController *childController;

}

@property (nonatomic, retain) NSArray *list;
@property (nonatomic, retain) NSString *selectedCategory;

@end

Topic List Controller.m

主题列表 Controller.m

#import "TopicListController.h"
#import "TopicAppDelegate.h"
#import "TopicDetailController.h"
#import "NSArray-MutableDeepCopy.h"
#import "TopicConstants.h"

@implementation TopicListController

@synthesize list;
@synthesize selectedCategory;

- (void)viewWillAppear:(BOOL)animated
{
    NSString *path = [[NSBundle mainBundle] pathForResource:@"TopicContent" ofType:@"plist"];

    NSMutableArray *fullArray = [[NSMutableArray alloc] initWithContentsOfFile:path];   
    NSMutableArray *fullArrayCopy = [fullArray mutableDeepCopy];

    NSUInteger items = [fullArrayCopy count];
    NSUInteger item=0;

        for (item; item /*less than*/ items; item++) {
            if ([[[fullArrayCopy objectAtIndex:item] objectForKey:CATEGORIES_KEY] 
             rangeOfString:selectedCategory 
             options:NSCaseInsensitiveSearch].location == NSNotFound) 
        {
            [fullArrayCopy removeObjectAtIndex:item];
            item--;
            items--;
        }
    }

    self.list = fullArrayCopy;
    [fullArray release];
    [self.tableView reloadData];
    [super viewWillAppear:animated];
}

- (void)viewDidUnload
{
    self.list = nil;
    self.selectedCategory = nil;
    [childController release];
    childController = nil;
}

- (void)dealloc
{
    [list release];
    [selectedCategory release];
    [childController release];
    [super dealloc];
}

#pragma mark -
#pragma mark Table Data Source Methods

- (NSInteger) tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger) section
{
    return [list count];
}

- (UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *) indexPath
{
    static NSString *DisclosureButtonCellIdentifier = @"DisclosureButtonCellIdentifier";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:DisclosureButtonCellIdentifier];

    if (cell==nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:DisclosureButtonCellIdentifier]
                autorelease];
    }

    NSUInteger row = [indexPath row];
    NSString *rowString = [[list objectAtIndex:row] objectForKey:TITLE_KEY];
    NSString *rowDetailString = [[list objectAtIndex:row] objectForKey:SUBTITLE_KEY];
    cell.textLabel.text = rowString;
    cell.detailTextLabel.text = rowDetailString;
    cell.accessoryType = UITableViewCellAccessoryDetailDisclosureButton;
    [rowString release];
    [rowDetailString release];
    return cell;
}

#pragma mark -
#pragma mark Table Delegate Methods

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (childController == nil) {
        childController = [[TopicDetailController alloc] initWithNibName:@"TopicDetail" bundle:nil];
    }


    NSUInteger row = [indexPath row];

    NSString *selectedTopicInformation = [[list objectAtIndex:row] objectForKey:INFORMATION_KEY];
    NSString *selectedTopicTitle = [[list objectAtIndex:row] objectForKey:TITLE_KEY];
    NSString *selectedTopicSubtitle = [[list objectAtIndex:row] objectForKey:SUBTITLE_KEY];
    NSString *selectedTopicTips = [[list objectAtIndex:row] objectForKey:TIPS_KEY];

    NSString *detailMessageInformation  = [[NSString alloc] initWithFormat:@"%@.", selectedTopicInformation];
    NSString *detailMessageTitle = [[NSString alloc] initWithFormat:@"%@", selectedTopicTitle];
    NSString *detailMessageSubtitle = [[NSString alloc] initWithFormat:@"%@", selectedTopicSubtitle];
    NSString *detailMessageTips = [[NSString alloc] initWithFormat:@"%@", selectedTopicTips];

    childController.messageInformation = detailMessageInformation;
    childController.messageTitle = detailMessageTitle;
    childController.messageSubTitle = detailMessageSubtitle;
    childController.messageTips = detailMessageTips;

    childController.title = @"Topic Detail";

    [detailMessageInformation release];
    [detailMessageTitle release];
    [detailMessageSubtitle release];
    [detailMessageTips release];
    [self.navigationController pushViewController:childController animated:YES];


}

- (void)tableView:(UITableView *)tableView accessoryButtonTappedForRowWithIndexPath:(NSIndexPath *)indexPath
{
    if (childController == nil) {
        childController = [[TopicDetailController alloc] initWithNibName:@"TopicDetail" bundle:nil];
    }

    NSUInteger row = [indexPath row];

    NSString *selectedTopicInformation = [[list objectAtIndex:row] objectForKey:INFORMATION_KEY];
    NSString *selectedTopicTitle = [[list objectAtIndex:row] objectForKey:TITLE_KEY];
    NSString *selectedTopicSubtitle = [[list objectAtIndex:row] objectForKey:SUBTITLE_KEY];
    NSString *selectedTopicTips = [[list objectAtIndex:row] objectForKey:TIPS_KEY];

    NSString *detailMessageInformation  = [[NSString alloc] initWithFormat:@"%@.", selectedTopicInformation];
    NSString *detailMessageTitle = [[NSString alloc] initWithFormat:@"%@", selectedTopicTitle];
    NSString *detailMessageSubtitle = [[NSString alloc] initWithFormat:@"%@", selectedTopicSubtitle];
    NSString *detailMessageTips = [[NSString alloc] initWithFormat:@"%@", selectedTopicTips];

    childController.messageInformation = detailMessageInformation;
    childController.messageTitle = detailMessageTitle;
    childController.messageSubTitle = detailMessageSubtitle;
    childController.messageTips = detailMessageTips;

    childController.title = @"Topic Detail";

    [detailMessageInformation release];
    [detailMessageTitle release];
    [detailMessageSubtitle release];
    [detailMessageTips release];
    [self.navigationController pushViewController:childController animated:YES];
}

@end

回答by Robert H?glund

Your problem is in tableView:cellForRowAtIndexPath:. You shouldn't release the following:

你的问题在tableView:cellForRowAtIndexPath:. 您不应该发布以下内容：

[rowString release];
[rowDetailString release];

when you get the string like:

当你得到这样的字符串时：

NSString *rowString = [[list objectAtIndex:row] objectForKey:TITLE_KEY];
NSString *rowDetailString = [[list objectAtIndex:row] objectForKey:SUBTITLE_KEY];

They are returned as autoreleased objects. You should only ever release something you own, i.e. something you have alloced, retained or gotten from a method starting with new. A good article explaining this is objective-c memory management for lazy people. But to quote the important part:

它们作为自动释放的对象返回。你应该只释放你拥有的东西，即你已经分配、保留或从一个以 new 开始的方法中获得的东西。一篇解释这一点的好文章是针对懒人的objective-c 内存管理。但要引用重要的部分：

• You own it if you alloc it.
• You own it if you copy it.
• You own it if you new it. (New is simply a shortcut for alloc/init).

• 如果你分配它，你就拥有它。
• 如果你复制它，你就拥有它。
• 如果你是新的，你就拥有它。（New 只是 alloc/init 的快捷方式）。