Question

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.

Answer 1

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!