我想在sqlite中创建一个新的实体(表).我的代码如下：
- +(BOOL)CreateDataSet:(NSManagedObjectModel *) model
- attributes:(NSDictionary*)attributes
- entityName:(NSString*) entityName
- {
- NSEntityDescription *entityDef = [[NSEntityDescription alloc] init];
- [entityDef setName:entityName];
- [entityDef setManagedObjectClassName:entityName];
- [model setEntities:[NSArray arrayWithObject:entityDef]];
- NSArray *properties = [CoreDataHelper CreateAttributes:attributes];
- [entityDef setProperties:properties];
- [entityDef release];
- return TRUE;
- }
但它会引发错误：
- Terminating app due to uncaught exception 'NSInternalInconsistencyException',reason: 'Can't modify an immutable model.'
- *** Call stack at first throw:
- (
- 0 CoreFoundation 0x01c5abe9 __exceptionPreprocess + 185
- 1 libobjc.A.dylib 0x01daf5c2 objc_exception_throw + 47
- 2 CoreData 0x0152634a -[NSManagedObjectModel(_NSInternalMethods) _throwIfNotEditable] + 106
- 3 CoreData 0x01526904 -[NSManagedObjectModel setEntities:] + 36
- ....
这似乎表明该模型是只读的.
解决方法
From the documentation:(重点是我的)
Managed object models are editable
until they are used by an object graph
manager (a managed object context or a
persistent store coordinator). This
allows you to create or modify them
dynamically. However,once a model is
being used,it must not be changed.
This is enforced at runtime—when the
object manager first fetches data
using a model,the whole of that model
becomes uneditable. Any attempt to
mutate a model or any of its
sub-objects after that point 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.
