ios-CoreData 對象充填NSSet

CoreData 對象充填NSSet

有一個CoreData中的一對多關系。現在想從coredata實體中創建一個對象，然後設置為NSSet。

我想實例化對象沒有錯，但是再設置NSSet時就不對。

AppDelegate *appDelegate = [[UIApplication sharedApplication]delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];

NSSet *selectedCategories = [NSSet set];

for (NSString *categoryName in self.categories /*NSMutableArray propterty*/) {
    Category *category = [NSEntityDescription  
    insertNewObjectForEntityForName:@"Category" inManagedObjectContext:context];
    category.name = categoryName;
    [selectedCategories setByAddingObject:category];
}

[self.delegate addCategoryViewControllerDidSelectCategory:
                                 self didSelectCategories:selectedCategories];

最佳回答：

這行：

[selectedCategories setByAddingObject:category];

創建了一個沒有指定變量的新設置，試試用NSMutableSet

NSMutableSet *selectedCategories = [NSMutableSet set];

for (NSString *categoryName in self.categories /*NSMutableArray propterty*/) {
    Category *category = [NSEntityDescription  
    insertNewObjectForEntityForName:@"Category" inManagedObjectContext:context];
    category.name = categoryName;
    [selectedCategories addObject:category];
}