iOS从数组导入的魔法记录 [英] iOS Magical record import from array

问题描述

您好，我收到 JSON 响应从服务器更新数据库的同步功能。如果有不同的数据（新记录或更新现有记录）（为了提高性能）（使用 coredata 和 magicalRecord ）

这是我的JSON解析器方法

   - （void）updateWithApiRepresentation：（NSDictionary *）json 
 {
 self.title = json [@Name]; 
 self.serverIdValue = [json [@Id] integerValue]; 
 self.year = json [@Year of Release]; 
 self.month = json [@Month of Release]; 
 self.day = json [@Day of Release]; 
 self.details = json [@Description]; 
 self.coverImage = json [@CoverImage]; 
 self.thumbnail = json [@Thumbnail]; 
 self.price = json [@Buy]; 
 
 NSDateFormatter * formatter = [[NSDateFormatter alloc] init]; 
 [formatter setDateFormat：@dd / MMMM / yyy]; 
 
 NSDate * date = [formatter dateFromString：[NSString stringWithFormat：@％@ /％@ /％@，self.day，self.month，self.year]]; 
 self.issueDate = date; 
} 
  

而我的导入方法

  +（void）API_getStampsOnCompletion：（void（^）（BOOL success，NSError * error））completionBlock 
 {
 [ApiClient sharedInstance] getStampsOnSuccess： （id responseJSON）{
 
 NSManagedObjectContext * localContext = [NSManagedObjectContext MR_context]; 
 NSMutableArray * stamps = [[NSMutableArray alloc] init]; 
 [responseJSON [@root] enumerateObjectsUsingBlock：^（id attributes，NSUInteger idx，BOOL * stop）{
 Stamp * stamp = [[Stamp alloc] init]; 
 [stamp setOrderingValue：idx]; 
 [stamp updateWithApiRepresentation：attributes]; 
 [stamps addObject：stamp]; 
}]; 
 
 [Stamp MR_importFromArray：stamps inContext：localContext]; 
 
} onFailure：^（NSError * error）{
 if（completionBlock）{
 completionBlock（NO，error）; 
} 
}]; 
} 
  

我收到错误

$ b $ CoreData：error：无法调用NSManagedObject类的指定初始化器
2016-08-02 23：52：20.216 SingPost [2078：80114] - [邮件setOrdering：]：无法识别的选择器发送到实例0x78f35a30


我检查了我的Json解析器工作正常。问题是我的导入方法。我不知道这个函数出了什么问题。任何帮助是非常感激。感谢！

解决方案

错误消息清楚地描述了确切的问题。你这样做：

  Stamp * stamp = [[Stamp alloc] init]; 
  

但 init 不是指定的初始值 NSManagedObject ，除非你在你的子类中添加了 init （你没有提到）。您必须调用指定的初始化程序，即 initWithEntity：insertIntoManagedObjectContext：。还有一个方便的工厂方法在 NSEntityDescription 调用 insertNewObjectForEntityForName：inManagedObjectContext：。任何一个都可以工作，但是调用 init 不会。

Hi I'm making a synchronise function that update database when receive JSON response from server. I want the import only take place if there are different data (new record or update existing record) (To increase performance) (Using coredata and magicalRecord)

Here is my JSON parser method

- (void)updateWithApiRepresentation:(NSDictionary *)json
{
    self.title = json[@"Name"];
    self.serverIdValue = [json[@"Id"] integerValue];
    self.year = json[@"Year of Release"];
    self.month = json[@"Month of Release"];
    self.day = json[@"Day of Release"];
    self.details = json[@"Description"];
    self.coverImage = json[@"CoverImage"];
    self.thumbnail = json[@"Thumbnail"];
    self.price = json[@"Buy"];

    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
    [formatter setDateFormat:@"dd/MMMM/yyy"];

    NSDate *date = [formatter dateFromString:[NSString stringWithFormat:@"%@/%@/%@",self.day,self.month,self.year]];
    self.issueDate = date;
}

And my import method

+ (void)API_getStampsOnCompletion:(void(^)(BOOL success, NSError     *error))completionBlock
{
    [[ApiClient sharedInstance] getStampsOnSuccess:^(id responseJSON) {

    NSManagedObjectContext *localContext = [NSManagedObjectContext MR_context];
    NSMutableArray *stamps = [[NSMutableArray alloc]init];
    [responseJSON[@"root"] enumerateObjectsUsingBlock:^(id attributes, NSUInteger idx, BOOL *stop) {
        Stamp *stamp = [[Stamp alloc]init];
        [stamp setOrderingValue:idx];
        [stamp updateWithApiRepresentation:attributes];
        [stamps addObject:stamp];
    }];

    [Stamp MR_importFromArray:stamps inContext:localContext];

} onFailure:^(NSError *error) {
        if (completionBlock) {
            completionBlock(NO, error);
        }
    }];
}

I'm getting error

CoreData: error: Failed to call designated initializer on NSManagedObject class 'Stamp' 
2016-08-02 23:52:20.216 SingPost[2078:80114] -[Stamp setOrdering:]: unrecognized selector sent to instance 0x78f35a30

I have checked my Json parser is working fine. The problem is with my import method. I don't know what wrong with the function. Any help is much appreciate. Thanks!

解决方案

The error message clearly describes the exact problem. You do this:

Stamp *stamp = [[Stamp alloc]init];

But init is not the designated initializer for NSManagedObject unless you added init in your subclass (which you didn't mention doing). You must call the designated initializer, which is initWithEntity:insertIntoManagedObjectContext:. There's also a convenience factory method on NSEntityDescription called insertNewObjectForEntityForName:inManagedObjectContext:. Either of those will work, but calling init will not.

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