核心数据：为什么我不能获取任何东西与我的谓词 [英] Core Data: why I can't fetch anything with my predicate

问题描述

代码有什么问题吗？我可以使用这个谓词没有任何东西。注释掉谓词，然后我可以从实体BankDetail获取所有对象。所以我认为问题存在于这两行。

  // self.bankInfo.name在prepareForSegue中设置在第一个视图控制器
 NSPredicate * predicate = [NSPredicate predicateWithFormat：@info.name =％@，self.bankInfo.name]; 
 [request setPredicate：predicate]; 
  

我的模型包含两个实体，它们是一对一关系

BankInfo.h

  @class BankDetail; 
 
 @interface BankInfo：NSManagedObject 
 
 @property（nonatomic，retain）NSString * city; 
 @property（nonatomic，retain）NSString * name; 
 @property（nonatomic，retain）NSString * state; 
 @property（nonatomic，retain）BankDetail * detail; 
 
 @end 
  

BankDetail.h

  @class BankInfo; 
 
 @interface BankDetail：NSManagedObject 
 
 @property（nonatomic，retain）NSString * closeDate; 
 @property（nonatomic，retain）NSString * updateDate; 
 @property（nonatomic，retain）NSString * zip; 
 @property（nonatomic，retain）NSString * acquireInstitution; 
 @property（nonatomic，retain）BankInfo * info; 
 
 @end 
  

EDIT： p>

提供更多详情：

• .bankInfo.name 是绝对设置的，我NSLog正好在谓词之前




• $ c> viewDidLoad ：

    NSEntityDescription * entity = [NSEntityDescription entityForName：@BankDetailinManagedObjectContext：上下文]; 
   NSLog（@[entity description] is％@，[entity description]）; 
    

  info =（），name信息，isOptional 1，isTransient 0，实体BankDetail，renamingIdentifier信息，验证谓词\ n），warningHashModifier（null）\\\
 userInfo {\ n}，目标实体BankInfo，inverseRelationship细节，minCount 1，maxCount 1，isOrdered 0，deleteRule 2; 
  

EDIT2：
出现与谓词。该错误是由其他地方的粗心错误引起的（见接受的答案，它是关于重命名）。如果您对谓词有疑问，请忽略此信息。

解决方案

我终于修复了错误。它不是关于谓词。我在Xcode编辑器中的.xcdatamodeld中将实体从 BankDetails 重命名为 BankDetail 重命名任何其他文件。

然后我手动重命名自动生成的NSManagedObject子类文件中的各个部分，以及引用它的其他类文件，直到所有警告消失。我想我已经重命名所有必要的，但我不是。程序不运行，因为我希望我在问题中描述，但没有错误，没有警告，Xcode只是编译和运行。

一段时间后，当我终于尝试重新生成子类文件来修复错误时，旧的 BankDetails 作为类名称，并出现了大量的命名错误。我认为这是Xcode的一些bug在第一。所以我清理生成和重新生成子类文件。然而，它仍然是好的旧 BankDetails 。经过几次尝试，我发现数据模型检查器中的问题（见下面的屏幕截图）。

道德：总是重新命名。 =https://i.stack.imgur.com/a2fzl.pngalt =输入图片说明here>>

Is there something wrong with the code? I can fetch nothing using this predicate. Comment out the predicate then I can fetch all objects from entity "BankDetail". So I think problem resides in these two lines.

// self.bankInfo.name is set in prepareForSegue in first view controller
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"info.name = %@",self.bankInfo.name];
[request setPredicate:predicate];

My model includes two entities, which are in one-to-one relationship

BankInfo.h

@class BankDetail;

@interface BankInfo : NSManagedObject

@property (nonatomic, retain) NSString * city;
@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) NSString * state;
@property (nonatomic, retain) BankDetail * detail;

@end

BankDetail.h

@class BankInfo;

@interface BankDetail : NSManagedObject

@property (nonatomic, retain) NSString * closeDate;
@property (nonatomic, retain) NSString * updateDate;
@property (nonatomic, retain) NSString * zip;
@property (nonatomic, retain) NSString * acquiringInstitution;
@property (nonatomic, retain) BankInfo * info;

@end

EDIT:

To provide more detail:

• self.bankInfo.name is definitely set, I NSLog it right before the line of predicate

• And I do this in viewDidLoad:

  NSEntityDescription *entity = [NSEntityDescription entityForName:@"BankDetail" inManagedObjectContext:context];
  NSLog(@"[entity description] is %@",[entity description]);
  

Get this in console:

info = "(<NSRelationshipDescription: 0x6d3eb30>), name info, isOptional 1, isTransient 0, entity BankDetail, renamingIdentifier info, validation predicates (\n), warnings (\n), versionHashModifier (null)\n userInfo {\n}, destination entity BankInfo, inverseRelationship detail, minCount 1, maxCount 1, isOrdered 0, deleteRule 2";

EDIT2: Turn out there's nothing wrong with the predicate. The bug is caused by a careless mistake elsewhere (see the accepted answer, it's about renaming). Please IGNORE this post if you have question about predicate.

解决方案

I finally fix the bug. It's not about the predicate at all. I rename the entity from BankDetails to BankDetail in .xcdatamodeld in Xcode editor by simply hit return key and change it, like renaming any other file.

Then I go ahead to manually rename various parts in the auto generated NSManagedObject subclass files, and in other class files that reference it, until all warnings go away. I think I have renamed all that are necessary, but I wasn't. The program doesn't run as I expect like I described in the question, but no error, no warning, Xcode just compile and run.

After some time, when I finally try to regenerate the subclass files to fix the bug, the old BankDetails shows up as class name, and lots of naming errors come out. I thought it was some bug of Xcode at first. So I clean the build and regenerate subclass files again. Yet, it's still the good old BankDetails. After a few attempts, I found the problem in Data Model Inspector (see screenshot below). Change the Class name and everything runs perfectly.

Moral: always rename in extreme caution!

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