Question

我需要在setter方法中做一些额外的事情。但是这样做我得到一个无限循环：

我有一个核心数据对象

@interface Transaction : NSManagedObject 
@property (nonatomic, retain) NSDate * date;
@end

@implementation Transaction
@dynamic date;

-(void)setDate:(NSDate *)date
{
    self.date = date;
    //additional stuff omitted
}

所以，在这种情况下，我得到一个无限循环。好的，所以我在网上搜索并按以下方式修改我的代码，并且每个版本都会出现编译错误

版本1：

@interface Transaction : NSManagedObject 
@property (nonatomic, retain) NSDate * date;
@end

@implementation Transaction
@dynamic date;

-(void)setDate:(NSDate *)date
{
    self->date = date; //Error: Property 'date' found on object 'Transaction *'; did you mean to access it with the "." operator?
    //additional stuff omitted
}

第2版：

@interface Transaction : NSManagedObject 
@property (nonatomic, retain) NSDate * date;
@end

@implementation Transaction
@dynamic date = _date; //Error: Expected ';' after @dynamic

-(void)setDate:(NSDate *)date
{
    _date = date; 
    //additional stuff omitted
}

现在，我问自己该怎么做？

Answer 1

我的问题的解决方案：

@interface Transaction : NSManagedObject 
@property (nonatomic, retain) NSDate * date;
@end

@implementation Transaction
@dynamic date;

-(void)setDate:(NSDate *)date
{
    [self setPrimitiveValue:date forKey:@"date"];
    //additional stuff omitted
}

Answer 2

“日期”是否由Core Data中的相应属性支持？

如果是，请查看Custom setter methods in Core-Data

如果没有，并且您不需要保留“日期”，则您的代码应如下所示：

@interface Transaction : NSManagedObject 
@property (nonatomic, retain) NSDate * date;
@end

@implementation Transaction
@synthesize date = _date;

-(void)setDate:(NSDate *)date
{
    _date = date; 
    //additional stuff omitted
}

Answer 3

以下是用于在不破坏KVO的情况下覆盖NSManagedObject属性的Apple方法：.m：

@interface Transaction (DynamicAccessors)
- (void)managedObjectOriginal_setDate:(NSDate *)date;
@end

@implementation Transaction
@dynamic date;

- (void)setDate:(NSDate *)date
{
    [self managedObjectOriginal_setDate:(NSString *)date;
    // your custom code
}

如本页底部What's New in Core Data in macOS 10.12, iOS 10.0, tvOS 10.0, and watchOS 3.0

所示

覆盖具有弧和动态属性的setter

3 个答案: