奇怪的 XCode 4.2 和核心数据行为
所以我最近升级到了 XCode 4.2，部分原因是我需要 IOS 5 SDK。
无论如何，当我编译并尝试运行我的应用程序时，我发现它不再运行。这是因为核心数据实体中的属性现在以某种方式标记为只读。
我没有这样做，除了错误消息之外我找不到任何证据。
在我的核心数据管理对象中，称为“注意：
@interface Note : NSManagedObject
@property (nonatomic, retain) NSString * title;
...
@implementation Note
@dynamic title;
...
稍后 - 以及其他地方 - 在代码中，我尝试执行以下操作：
self.note.title=self.noteTitle.text;
当执行到此行时，我收到这些错误：
Property 'title' is marked readonly on class 'Note'. Cannot generate a setter method for it.
-[Note setTitle:]: unrecognized selector sent to instance 0x80ae3d0
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Note setTitle:]: unrecognized selector sent to instance 0x80ae3d0'
什么？？？？我可以手动编码设置器 - 错误表明它无法为我生成一个设置器 - 但我真的很想了解这里发生了什么。
我确实为该实体重新生成了托管对象文件，但这不起作用。我也创建了一个新的数据模型，并检查以确保没有设置任何不应该设置的内容。
编辑：我遗漏了一个重要的花絮：我在 Note（托管对象）上定义了一个类别。在类别中，我向对象添加了协议（MKAnnotation）。我的类别是这样定义的：
@interface Note (Extras) <MKAnnotation>
我已经删除了协议的“需要”，但没有删除引用。当我这样做时，一切都回到了应有的样子。
因此，虽然我已经解决了我的问题，但我还是想知道：向托管对象添加协议是不是不好的行为？
谢谢。
So I recently upgraded to XCode 4.2, in part because I needed the IOS 5 SDK.
Anyhow, when I compiled and attempted to run my app, I found that it would no longer run. This is due to the fact that an attribute in a Core Data entity is now somehow marked as read only.
I did not do this, and I can find no evidence of this other than the error message.
In my core data managed object, called Note:
@interface Note : NSManagedObject
@property (nonatomic, retain) NSString * title;
...
@implementation Note
@dynamic title;
...
Later - and elsewhere - in the code, I attempt to do this:
self.note.title=self.noteTitle.text;
When execution gets to this line, I receive these errors:
Property 'title' is marked readonly on class 'Note'. Cannot generate a setter method for it.
-[Note setTitle:]: unrecognized selector sent to instance 0x80ae3d0
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Note setTitle:]: unrecognized selector sent to instance 0x80ae3d0'
What the ???? I could just hand-code the setter - the error says it cannot generate one for me - but I'd really like to understand what happened here.
I did regenerate the managed object files for this entity, which did not work. I created a new data model, too, and checked to make sure nothing was set that shouldn't be.
Edit: I left out what turned out to be an important tidbit: I have a category defined on Note (the managed object). In the category, I added a protocol to the object (MKAnnotation). My category was defined thusly:
@interface Note (Extras) <MKAnnotation>
I had since removed the 'need' for the protocol, but did not remove the reference. When I did, everything went back to the way it should be.
So while I've solved my problem, I'm left wondering: Is it bad behavior to add a protocol to a managed object?
Thanks.
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MKAnnotation协议有一个只读title属性：.. 它与同名的动态属性冲突。
（来源：Apple，MKAnnotation 协议参考)
The
MKAnnotationprotocol has a readonlytitleproperty:.. which conflicts with your dynamic property by the same name.
(Source: Apple, MKAnnotation Protocol Reference)
将协议添加到 NSManagedObject 中也不错；您想要这样做的原因有很多。
It is not bad to add protocols to a
NSManagedObject; there are many reasons why you would want to.