使用Core Data存储自定义对象 [英] Storing custom objects with Core Data

问题描述

我试图存储一个由VOs（NameVO）与Core Data组成的NSMutableArray，但是会抛出以下异常：

 'NSInvalidArgumentException'，reason：' -  [NameVO encodeWithCoder：]：无法识别的选择器发送到实例0x1096400a0'
  

我的NameVO只是一个简单的值对象，扩展NSObject并包含两个字段，一个字符串和一个NSMutableArray本身包含字符串。它还包含一个比较函数。

我试图准备这个存储为一个CD可变属性类型（'names'是我的NameVO数组）：

  NSData * tempNamesData = [NSKeyedArchiver archivedDataWithRootObject：names]; 
  

我的问题是：我需要做什么来使NameVO被NSKeyedArchiver接受才能成功到NSData？

我不想让NameVO扩展NSManagedObject，因为我不能直接实例化和初始化。

NSCoding 协议到你的类，你必须重写两个方法：

   - （void）encodeWithCoder：（NSCoder *）aCoder; 
  - （id）initWithCoder：（NSCoder *）aDecoder; 
  

应该排序您的问题。

// EXTENDED

   - （id）initWithCoder：（NSCoder *）aDecoder 
 {
 self = [ super init]; 
 if（self）{
 _formId = [aDecoder decodeObjectForKey：@FormID]; 
} 
 return self; 
} 
 
  - （void）encodeWithCoder：（NSCoder *）aCoder 
 {
 [aCoder encodeObject：self.formId forKey：@FormID]; 
} 
  

I'm trying to store a NSMutableArray consisting of VOs (NameVO) with Core Data but getting the following exception thrown:

'NSInvalidArgumentException', reason: '-[NameVO encodeWithCoder:]: unrecognized selector sent to instance 0x1096400a0'

My NameVO is just a simple value object, extending NSObject and contains two fields, a string and a NSMutableArray that itself contains strings. It also contains a compare function.

I'm trying to prepare this to be stored as a CD transformable attribute type with ('names' is my NameVO array):

NSData *tempNamesData = [NSKeyedArchiver archivedDataWithRootObject:names];

My question is: what do I need to do to make NameVO be accepted by NSKeyedArchiver to convert it successfully to a NSData?

I don't want NameVO to extend NSManagedObject because then I cannot instantiate and init it directly.

解决方案

As your exception says you need to implement NSCoding protocol to your class and you have to override two methods:

- (void)encodeWithCoder:(NSCoder *)aCoder;
- (id)initWithCoder:(NSCoder *)aDecoder;

It should sorted your issue.

// EXTENDED

- (id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super init];
    if (self) {
        _formId = [aDecoder decodeObjectForKey:@"FormID"];
    }
    return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:self.formId forKey:@"FormID"];
}

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