无法在iOS上创建受管对象上下文 [英] Cannot create a managed object context on iOS
问题描述
我创建了一个非核心数据项目。我现在想使用核心数据。在构建阶段,我将我的二进制文件与CoreData.framework链接。在我的应用程序委托方法,我想手动创建一个托管对象上下文,像这样
NSManagedObjectContext * aContext = [[NSManagedObjectContext alloc]在里面];
当我执行上述操作时,会收到以下错误:
类消息的Receiver'NSManagedObjectContext'是一个forward声明。对于我可能做错了什么建议? =h2_lin>解决方案您需要在应用程序委托的头文件中导入CoreData / CoreData.h:
#import< CoreData / CoreData.h>
因为你可能通过outyour应用程序使用它,你应该把它放在预编译的头文件中,YourApp-Prefix .pch:
#ifdef __OBJC__
#import< UIKit / UIKit.h>
#import< Foundation / Foundation.h>
#import< CoreData / CoreData.h>
#endif
I created a non core data project. I now want to use core data. In the build phases, I linked my binary with CoreData.framework. In my application delegate method, I want to manually create a managed object context like so
NSManagedObjectContext *aContext = [[NSManagedObjectContext alloc] init];
When I do the above, I get the following error,
Receiver 'NSManagedObjectContext' for class message is a forward declaration.
Any suggestions on what I might be doing wrong?
解决方案 You need to import CoreData/CoreData.h in your application delegate's header file:
#import <CoreData/CoreData.h>
Since you probably use it through outyour application you should put it in the precompiled header file, YourApp-Prefix.pch:
#ifdef __OBJC__
#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
#endif
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