核心数据崩溃不可变对象

为什么会崩溃？核心数据崩溃不可变对象

CategoryOfExpense *newCatEx = (CategoryOfExpense *) [NSEntityDescription entityForName:kCategoryOfExpense inManagedObjectContext:moc]; 
newCatEx.name = self.nameTextField.text; <- crashes here 
newCatEx.icon = [NSData dataWithData:UIImagePNGRepresentation(self.iconImageView.image)];

的错误是：

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Can't modify an immutable model.'

来源

2012-09-07 user1028028

您是否在尝试访问其成员变量之前检查newCatEx是否不为零？ – mark

这不是零.... – user1028028

您正在致电entityForName:inManagedObjectContext:，它返回NSEntityDescription。这将是实体的定义，就像您在构建模型时在GUI中描述的那样。

我相信你想要的是insertNewObjectForEntityForName:inManagedObjectContext:这将创建一个新的实体NSManagedObject。

来源

2012-09-07 20:24:33

是的..这就是我正在做 – user1028028

试试这个：

您可以通过调用的NSManagedObjectModel实例-mutableCopy得到模型的可变副本。

发现这里How to edit a NSManagedObjectModel that was loaded from a momd in iOS5

来源

2012-09-07 18:45:12 mark

我没有使用模型...只是NSManagedObjectContext ... – user1028028

你就错了。这是从dev site：

编辑实体描述：

Entity descriptions are editable until they are used by an object graph manager. 
This allows you to create or modify them dynamically. 
However, once a description is used (when the managed object model to which it belongs 
is associated with a persistent store coordinator), it must not (indeed cannot) be changed. 
This is enforced at runtime: any attempt to mutate a model or any of its sub-objects 
after the model is associated with a persistent store coordinator causes an exception to 
be thrown. If you need to modify a model that is in use, create a copy, modify the copy, 
and then discard the objects with the old model.

接近尾声提到的例外是你会得到什么。进一步走向最后是你需要做的。

来源

2012-09-07 19:12:45 tipycalFlow

核心数据崩溃不可变对象

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