CoreData 对象充填NSSet

Question

有一个CoreData中的一对多关系。现在想从coredata实体中创建一个对象，然后设置为NSSet。

我想实例化对象没有错，但是再设置NSSet时就不对。

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];

Answer 1

这行：

[selectedCategories setByAddingObject:category];

创建了一个没有指定变量的新设置，试试用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];
}