ios [__NSArrayM objectAtIndex:] 崩溃：索引 0 超出空数组错误的界限
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Crashes with [__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array error
提问by msetten
I am getting crash reports via users of my iOS app, but crash I can't reproduce myself, nor can I trace the error back to a line in my own code (except that it originates from line 14 in main.m but this is the default application creation of iOS apps. Below the a crash report I received.
我通过我的 iOS 应用程序的用户收到崩溃报告，但崩溃我无法重现，我也无法将错误追溯到我自己代码中的一行（除了它源自 main.m 中的第 14 行，但这是iOS 应用程序的默认应用程序创建。下面是我收到的崩溃报告。
In understand that at some point a object is at index 0 is being retrieved from an empty Array. But since it doesn't seem to point to my own code, can it be a bug in iOS? (It happens on different platforms and with different iOS versions).
据了解，在某个时候，正在从空数组中检索索引为 0 的对象。但是既然好像没有指向我自己的代码，那会不会是iOS的bug？（它发生在不同的平台和不同的 iOS 版本上）。
I hope someone has an idea what is happening or can point me in the right direction. Thanks.
我希望有人知道发生了什么，或者可以为我指明正确的方向。谢谢。
CRASH REPORT:
崩溃报告：
Incident Identifier: [TODO]
CrashReporter Key: [TODO]
Process: Mary Black [797]
Path: /var/mobile/Applications/28A68F8B-294E-4B86-9E75-ED5484E5EF4D/Mary Black.app/Mary Black
Identifier: net.broset.Mary-Black
Version: 225
Code Type: ARM (Native)
Parent Process: launchd [1]
Date/Time: 2011-10-14 03:47:32 +0000
OS Version: iPhone OS 5.0 (9A334)
Report Version: 104
Exception Type: SIGTRAP
Exception Codes: #0 at 0x35b07848
Crashed Thread: 0
Application Specific Information:
*** Terminating app due to uncaught exception \\'NSRangeException\\', reason: \\'*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array\\'
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x00010848 __kill + 8
1 CoreFoundation 0x000b9987 __handleUncaughtException + 75
2 libobjc.A.dylib 0x000092d1 _objc_terminate + 129
3 libc++abi.dylib 0x000043c5 _ZL19safe_handler_callerPFvvE + 77
4 libc++abi.dylib 0x00004451 operator delete(void*) + 1
5 libc++abi.dylib 0x00005825 __cxa_current_exception_type + 1
6 libobjc.A.dylib 0x00009235 objc_exception_rethrow + 13
7 CoreFoundation 0x0000f545 CFRunLoopRunSpecific + 405
8 CoreFoundation 0x0000f3a5 CFRunLoopRunInMode + 105
9 GraphicsServices 0x00003fed GSEventRunModal + 157
10 UIKit 0x00031743 UIApplicationMain + 1091
11 Mary Black 0x00002fa7 main (main.m:14)
回答by maz
One way to debug this issue is to add a Symbolic Breakpoint on objectAtIndex: This may result in manyhits to objectAtIndex: before the debugger hits the one you're after but it's guaranteed to find it.
调试此问题的一种方法是在 objectAtIndex 上添加一个符号断点：这可能会导致对 objectAtIndex 的多次点击：在调试器点击您要查找的那个之前，但它可以保证找到它。
Steps in Xcode 4:
Xcode 4 中的步骤：
- View > Navigators > Breakpoint Navigator
- click '+' and choose Add Symbolic Breakpoint in the pop-up
- type in "objectAtIndex:" in the Symbol text field and click Done
- 视图 > 导航器 > 断点导航器
- 单击“+”并在弹出窗口中选择“添加符号断点”
- 在符号文本字段中输入“objectAtIndex:”，然后单击完成
at runtime, if you can't tell which objectAtIndex: you're hitting, move the slider at the bottom of the Debug Navigator all the way to the right.
在运行时，如果您无法分辨您正在点击哪个 objectAtIndex:，请将 Debug Navigator 底部的滑块一直向右移动。
回答by Michael Superczynski
This will stop the debugger at the offending line:
这将在违规行停止调试器：
Xcode/Edit Scheme/Diagnostics/Log Exceptions.
Xcode/编辑方案/诊断/日志异常。
回答by vikingosegundo
This error means, that you try to get an object from a NSArray from a position where no object is found. In other words: if the index is 0, than your array is empty.
And most likely it is your code, as main() invokes your code.
此错误意味着，您尝试从未找到对象的位置从 NSArray 获取对象。换句话说：如果索引为 0，则您的数组为空。
并且很可能是您的代码，因为 main() 调用您的代码。
回答by alexantd
You need to search your project for all usages of objectAtIndex:and rule out each one as the culprit. Make sure you are nevercalling it on an empty array.
您需要在您的项目中搜索所有用法objectAtIndex:并排除每一种都是罪魁祸首。确保您永远不会在空数组上调用它。
Another tip: If you know you only want to get the last object in an array, oryou know the array will only ever contain one object, you can use lastObjectinstead of objectAtIndex:-- it's safer because it won't throw an exception, though you still need to check for nil.
另一个提示：如果您知道只想获取数组中的最后一个对象，或者您知道该数组将只包含一个对象，则可以使用lastObject代替objectAtIndex:-- 它更安全，因为它不会抛出异常，尽管您仍然需要检查nil.
