ios – 如何通过CoreData模型创建一个新的实体(表)？

概述我想在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 *entityD 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.

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