Exception thrown in NSOrderedSet generated accesso

Question

On my Lion app, I have this data model:

The relationship subitems inside Item is ordered.

Xcode 4.1 (build 4B110) has created for me the file Item.h, Item.m, SubItem.h and SubItem.h.

Here is the content (autogenerated) of Item.h:

#import <Foundation/Foundation.h>

#import <CoreData/CoreData.h>

@class SubItem;

@interface Item : NSManagedObject {
@private
}

@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) NSOrderedSet *subitems;
@end

@interface Item (CoreDataGeneratedAccessors)

- (void)insertObject:(SubItem *)value inSubitemsAtIndex:(NSUInteger)idx;
- (void)removeObjectFromSubitemsAtIndex:(NSUInteger)idx;
- (void)insertSubitems:(NSArray *)value atIndexes:(NSIndexSet *)indexes;
- (void)removeSubitemsAtIndexes:(NSIndexSet *)indexes;
- (void)replaceObjectInSubitemsAtIndex:(NSUInteger)idx withObject:(SubItem *)value;
- (void)replaceSubitemsAtIndexes:(NSIndexSet *)indexes withSubitems:(NSArray *)values;
- (void)addSubitemsObject:(SubItem *)value;
- (void)removeSubitemsObject:(SubItem *)value;
- (void)addSubitems:(NSOrderedSet *)values;
- (void)removeSubitems:(NSOrderedSet *)values;

@end

And here is the content (autogenerated) of Item.m:

#import "Item.h"
#import "SubItem.h"

@implementation Item

@dynamic name;
@dynamic subitems;

@end

As you can see, the class Item offers a method called addSubitemsObject:. Unfortunately, when trying to use it in this way:

Item *item = [NSEntityDescription insertNewObjectForEntityForName:@"Item" inManagedObjectContext:self.managedObjectContext];
item.name = @"FirstItem";

SubItem *subItem = [NSEntityDescription insertNewObjectForEntityForName:@"SubItem" inManagedObjectContext:self.managedObjectContext];

[item addSubitemsObject:subItem];

this error appear:

2011-09-12 10:28:45.236 Test[2002:707] *** -[NSSet intersectsSet:]: set argument is not an NSSet

Can you help me?

Update:

After just 1,787 days from my bug report, today (August 1, 2016) Apple wrote me this: "Please verify this issue with the latest iOS 10 beta build and update your bug report at bugreport.apple.com with your results.". Let's hope this is the right time :)

Answer 1

I think everybody is missing the real problem. It is not in the accessor methods but rather in the fact that NSOrderedSet is not a subclass of NSSet. So when -interSectsSet: is called with an ordered set as argument it fails.

NSOrderedSet* setA = [NSOrderedSet orderedSetWithObjects:@"A",@"B",@"C",nil];
NSSet* setB = [NSSet setWithObjects:@"C",@"D", nil];

 [setB intersectsSet:setA];

fails with *** -[NSSet intersectsSet:]: set argument is not an NSSet

Looks like the fix is to change the implementation of the set operators so they handle the types transparently. No reason why a -intersectsSet: should work with either an ordered or unordered set.

The exception happens in the change notification. Presumably in the code that handles the inverse relationship. Since it only happens if I set an inverse relationship.

The following did the trick for me

@implementation MF_NSOrderedSetFixes

+ (void) fixSetMethods
{
    NSArray* classes = [NSArray arrayWithObjects:@"NSSet", @"NSMutableSet", @"NSOrderedSet", @"NSMutableOrderedSet",nil];

    [classes enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        NSString* name = obj;
        Class aClass = objc_lookUpClass([name UTF8String]);
        [MF_NSOrderedSetFixes fixMethodWithSetArgument:@selector(intersectsSet:) forClass:aClass];
        [MF_NSOrderedSetFixes fixMethodWithSetArgument:@selector(isSubsetOfSet:) forClass:aClass];
    }];
}

typedef BOOL (*BoolNSetIMP)(id _s,SEL sel, NSSet*);

/*
    Works for all methods of type - (BOOL) method:(NSSet*) aSet
*/
+ (void) fixMethodWithSetArgument:(SEL) aSel forClass:(Class) aClass 
{
    /* Check that class actually implements method first */
    /* can't use get_classInstanceMethod() since it checks superclass */
    unsigned int count,i;
    Method method = NULL;
    Method* methods = class_copyMethodList(aClass, &count);
    if(methods) {
        for(i=0;i<count;i++) {
            if(method_getName(methods[i])==aSel) {
                method = methods[i];
            }
        }
        free(methods);
    }
    if(!method) {
        return;
    }

   // Get old implementation
   BoolNSetIMP originalImp  = (BoolNSetIMP) method_getImplementation(method);
   IMP newImp = imp_implementationWithBlock(^BOOL(NSSet *_s, NSSet *otherSet) {
        if([otherSet isKindOfClass:[NSOrderedSet class]]) {
            otherSet = [(NSOrderedSet*)otherSet set];
        }
        // Call original implementation
        return originalImp(_s,aSel,otherSet);
    });
    method_setImplementation(method, newImp);
}
@end

Answer 2

Yes, this is definitely a Core Data bug. I wrote up an ObjC-Runtime-based fix a while back, but at the time I figured it would be fixed soon. Anyway, no such luck, so I posted it up on GitHub as KCOrderedAccessorFix. Work around the problem on all your entities:

[managedObjectModel kc_generateOrderedSetAccessors];

One entity in particular:

[managedObjectModel kc_generateOrderedSetAccessorsForEntity:entity];

Or just for one relationship:

[managedObjectModel kc_generateOrderedSetAccessorsForRelationship:relationship];

Answer 3

Instead to making a copy I suggest to use the accessor in NSObject to get access to the NSMutableOrderedSet of the relationships.

- (void)addSubitemsObject:(SubItem *)value {
      NSMutableOrderedSet* tempSet = [self mutableOrderedSetValueForKey:@"subitems"];
      [tempSet addObject:value];
 }

e.g. the Core Data Release Notes for iOS v5.0 refer to this.

In a short test it worked in my application.

Answer 4

Better version of the correct answer in SWIFT

var tempSet = NSMutableOrderedSet()
if parent!.subItems != nil {
    tempSet = NSMutableOrderedSet(orderedSet: parent!.subItems!)
}

tempSet.add(newItem)
parent!.subItems = tempSet

Answer 5

The Apple docs To Many Relations says: you should access the proxy mutable set or ordered set using

NSMutableOrderedSet * set = [managedObject mutableOrderedSetValueForKey:@"toManyRelation"];

Modifying this set will add or remove relations to your managed object. Accessing the mutable ordered set using the accessor whether with [ ] or . notation is wrong and will fail.

Answer 6

If you are using mogenerator, then instead of

[parentObject add<Child>sObject:childObject];

simply use:

[[parent object <child>sSet] addObject:childObject];