XCode：异常。如何检测原因？ [英] XCode: Exception. How to detect the cause?

问题描述

使用iOS 6.1的Xcode 4.6.1。我正在使用与StackMob的远程数据库。应用程序首先发出错误，并且在单击播放几次后，它运行正常，并与服务器进行通信。不知道如何检测问题，应该怎么关心？

我有以下异常断点设置：

应用程序运行，然后停止在以下行：
< img src =https://i.stack.imgur.com/j5ZLH.pngalt =enter image description here>

  NSFetchRequest * fetchRequest = [[NSFetchRequest alloc] init]; 
 NSEntityDescription * entity = [NSEntityDescription entityForName：@UserinManagedObjectContext：self.managedObjectContext]; 
 [fetchRequest setEntity：entity]; 
 
 NSPredicate * predicate = [NSPredicate predicateWithFormat：@email ==％@，self.emailAddressField.text]; 
 [fetchRequest setPredicate：predicate]; 
 
 NSError * error = nil; 
 NSArray * fetchedObjects = [[self managedObjectContext] executeFetchRequest：fetchRequest error：& error]; 
  

所以我将上面的行改为：

  NSFetchRequest * fetchRequest = [[NSFetchRequest alloc] init]; 
 NSEntityDescription * entity = [NSEntityDescription entityForName：@UserinManagedObjectContext：self.managedObjectContext]; 
 [fetchRequest setEntity：entity]; 
 
 NSPredicate * predicate = [NSPredicate predicateWithFormat：@username ==％@，self.usernameField.text]; 
 [fetchRequest setPredicate：predicate]; 
 
 [managedObjectContext executeFetchRequest：fetchRequest onSuccess：^（NSArray * fetchedObjects）
 {
  

现在，当我运行程序，我得到以下错误：

与

所以我点击播放按钮

我收到以下错误：

之后，再次单击播放一次，应用程序继续运行，好像没有发生任何事情？我应该担心吗

解决方案

一旦调试器停止异常，您可以使用简单的lldb命令检查异常。在这里选择你的线程6中的异常：

然后，如果您正在运行模拟器类型：

 code> po $ eax 
  

如果您正在设备上运行：

  po $ r0（32位）
 po $ x0（64位）
  

您应该了解该例外情况。

Xcode 4.6.1 with iOS 6.1. I'm using remote database with StackMob. Application first gives an error and after I click Play a few times, it runs fine and communicates with the server just fine. Not sure how to detect the problem and should it a concern?

I have the following exception Break Point setup:

The application runs and then stops at the following line:

   NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"User" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"email == %@", self.emailAddressField.text];
    [fetchRequest setPredicate:predicate];

    NSError *error = nil;
    NSArray *fetchedObjects = [[self managedObjectContext] executeFetchRequest:fetchRequest error:&error];

so I changed the line above to:

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        NSEntityDescription *entity = [NSEntityDescription entityForName:@"User" inManagedObjectContext:self.managedObjectContext];
        [fetchRequest setEntity:entity];

        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"username == %@", self.usernameField.text];
        [fetchRequest setPredicate:predicate];

        [managedObjectContext executeFetchRequest:fetchRequest onSuccess:^(NSArray *fetchedObjects)
            {

Now when I run the program, I get the following error:

with

so I click the play button

and I get the following error:

and after I click play one more time, the Application continues to run as if nothing happened? Should I be concerned?

解决方案

You can check what the exception is with a simple lldb command, once the debugger stops on the exception. Select the exception like in your thread 6 here:

And then if you are running on the simulator type:

po $eax

If you are running on the device:

po $r0  (for 32-bit)
po $x0  (for 64-bit)

You should get a description of the exception.

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