CODEWITHSUNDEEP
ioscore-data
Mina
Mina

Reputation: 1516

iOS Core Data - Add related data to entity

iOS beginner here.

Given an entity with a Many-to-Many relationship

@class Categories;

@interface Events : NSManagedObject

@property (nonatomic, retain) NSString * title;
@property (nonatomic, retain) NSSet *categories;
@end

@interface Events (CoreDataGeneratedAccessors)

- (void)addCategoriesObject:(Categories *)value;
- (void)removeCategoriesObject:(Categories *)value;
- (void)addCategories:(NSSet *)values;
- (void)removeCategories:(NSSet *)values;

@end

Which is related to

@interface Categories : NSManagedObject

@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) NSManagedObject *events;

@end

And having some JSON data to populate the Events table

[{"title": "Test Exhibition", "categories": [{"name": "Exhibitions"}]}, {...}]

How should I format the JSON data to do something like

// Parse Events JSON
[events enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
...
Events *event = [NSEntityDescription
    insertNewObjectForEntityForName:@"Events" inManagedObjectContext:context];
event.title = [obj objectForKey:@"title"];
NSSet *categories = [[[NSSet alloc] init] setByAddingObjectsFromArray:[obj objectForKey:@"categories"]];
NSLog(@"CATS %@", categories);
[event addCategories:categories];

to eventually get Core Data to find the relative Category (already added to the database) and attach it to the Event?

At the moment I get

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFDictionary entity]: unrecognized selector sent to instance 0x893a8c0'

Any help will be much appreciated, thanks!

Upvotes: 0

Views: 145

Answers (1)

Arek Holko
Arek Holko

Reputation: 9006

categories is an NSSet of NSDictionaries, but

- (void)addCategories:(NSSet *)values;

expects an NSSet of NSManagedObject's. So, you have to create an NSManagedObject from each dictionary that describes a category, add them to a new NSSet (or NSMutableSet) and only then call addCategories: with the new set.

Upvotes: 1

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