Question

我有一个显示联系人列表的数据表。当我启动应用程序时，所有数据都已正确加载。但是在选择联系人后，我有时会遇到此异常： -

Program received signal: “EXC_BAD_ACCESS”. 有时候

-[UITableViewRowData isEqualToString:]: unrecognized selector sent to instance 0x391dce0

最有可能是这段代码： -

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {



static NSString *CellIdentifier = @"Cell";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

if (cell == nil) {

    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];

}
ExpenseTrackerAppDelegate *appDelegate = (ExpenseTrackerAppDelegate *)[[UIApplication sharedApplication] delegate];


Person *person = (Person *)[appDelegate.expensivePersonsList objectAtIndex:indexPath.row];

NSString *name = [NSString stringWithFormat:@"%@ %@" ,person.lastName , person.firstName];

static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } ExpenseTrackerAppDelegate *appDelegate = (ExpenseTrackerAppDelegate *)[[UIApplication sharedApplication] delegate];

如果我替换这些代码行

cell.textLabel.text = name; return cell; }

使用此代码 NSString *name = [NSString stringWithFormat:@"%@ %@" ,person.lastName , person.firstName]; cell.textLabel.text = name;

然后一切正常吗？

我不知道究竟发生了什么？在查看和调试后，我发现这段代码似乎无法正常工作。 cell.textLabel.text = person.lastName;


- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

// RootViewController *detailViewController = [[RootViewController alloc] initWithNibName:@"RootViewController" bundle:[NSBundle mainBundle]];
 PersonnalDetails *detailViewController = [[PersonnalDetails alloc] initWithNibName:@"PersonnalDetails" bundle:[NSBundle mainBundle]];
//detailViewController.view = [[UITableView alloc] initWithNibName:@"PersonnalDetails" bundle:[NSBundle mainBundle]];
 // ...
 // Pass the selected object to the new view controller.
    ExpenseTrackerAppDelegate *appDelegate = (ExpenseTrackerAppDelegate *)[[UIApplication sharedApplication] delegate];
NSInteger row = indexPath.row;
Person *person = [[appDelegate expensivePersonsList] objectAtIndex:row];
NSLog(@"%@", person.firstName);
  detailViewController.selectedPerson = person;
 [self.navigationController pushViewController:detailViewController animated:YES];
 [detailViewController release];

这条线

// RootViewController *detailViewController = [[RootViewController alloc] initWithNibName:@"RootViewController" bundle:[NSBundle mainBundle]];
 PersonnalDetails *detailViewController = [[PersonnalDetails alloc] initWithNibName:@"PersonnalDetails" bundle:[NSBundle mainBundle]];
//detailViewController.view = [[UITableView alloc] initWithNibName:@"PersonnalDetails" bundle:[NSBundle mainBundle]];
 // ...
 // Pass the selected object to the new view controller.
    ExpenseTrackerAppDelegate *appDelegate = (ExpenseTrackerAppDelegate *)[[UIApplication sharedApplication] delegate];
NSInteger row = indexPath.row;
Person *person = [[appDelegate expensivePersonsList] objectAtIndex:row];
NSLog(@"%@", person.firstName);
  detailViewController.selectedPerson = person;
 [self.navigationController pushViewController:detailViewController animated:YES];
 [detailViewController release];

抛出EXC_BAD_ACESS。我调试了代码，列表

包含对象。任何人都可以告诉我可能的原因吗？

Answer 1

我想你想为“objc_exception_throw”设置一个符号断点，这样你就可以看到崩溃前会发生什么。只需转到“运行”菜单 - ＆gt;管理断点 - ＆gt;添加符号断点，并键入objc_exception_throw。

BTW，您可能正在调用已删除的对象。

Answer 2

EXC_BAD_ACCESS上的调用堆栈是什么？

另外，你可以使用NSString来获取格式化的字符串，不需要使用NSMutableString或者转换它......

Answer 3

最后，我发现了问题。实际上，我想要做的是将Person对象的所有属性设置为只读，这样只有在init方法中才会初始化属性。所以Person.h看起来像：

@interface Person : NSObject {  
        NSInteger  pid;  
        NSString const *firstName;  
        NSString const *lastName;  
        NSString const *phoneNumber;  
        NSString const *emailAddress;  
}  

@property (readonly) NSString *firstName;  
@property (readonly) NSString *lastName;  
@property (readonly) NSString *phoneNumber;  
@property (readonly) NSString *emailAddress;  
@property (readonly) NSInteger pid;    

-(id)initWithName:(NSString *)n lastName:(NSString *)l phoneNumber:(NSString *)p emailAddress:(NSString *)e pid:(NSInteger)i;  
@end

并且所有这些值都没有保留这些值。

这个问题是我所有错误的主要问题： Initializing a readonly property

- [UITableViewRowData isEqualToString：]：无法识别的选择器发送到实例0x391dce0

3 个答案: