关于ios:类类别中的方法不作为实例方法工作

Method in class category works not as instance method

在我的项目中，我有两个NSManageObjects(生成的核心数据)。对于这两个对象，我都用名为containsToday的实例方法创建了一个类别。

问题是只有对象ListElement的方法有效。在调用对象NamedRange的方法时，我得到了(与类方法相同的方法)：

-[NSManagedObject containsToday]: unrecognized selector sent to instance ...

下面是一些代码：

ListElement：

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#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>

@class ListImage, TLList;

@interface ListElement : NSManagedObject

@property (nonatomic, retain) NSString * agn;
@property (nonatomic, retain) NSString * aid;
@property (nonatomic, retain) NSString * date;
@property (nonatomic, retain) NSString * iid;
@property (nonatomic, retain) NSNumber * indx;
@property (nonatomic, retain) NSNumber * mark;
@property (nonatomic, retain) NSString * oid;
@property (nonatomic, retain) NSString * tcd;
@property (nonatomic, retain) NSString * ted;
@property (nonatomic, retain) NSNumber * cxl;
@property (nonatomic, retain) NSString * oti;
@property (nonatomic, retain) ListImage *listImage;
@property (nonatomic, retain) TLList *tlList;

@end

NamedRange：

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#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>

@interface NamedRange : NSManagedObject

@property (nonatomic, retain) NSString * tid;
@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) NSString * sta;
@property (nonatomic, retain) NSString * end;

@end

ListElement(添加项)：

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#import"ListElement.h"

@interface ListElement (Additions)

- (BOOL) containsToday;

@end

名称范围(添加)：

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#import"NamedRange.h"

@interface NamedRange (Additions)

#warning TODO - why does this not work as instance method (for ListElement it works)?
+ (BOOL) containsToday:(NamedRange*)nr;
- (BOOL) containsToday;
@end