MTLManagedObjectAdapter.m

// MTLManagedObjectAdapter.m

- (NSPredicate *)uniquingPredicateForModel:(MTLModel<MTLManagedObjectSerializing> *)model {
  NSSet *propertyKeys = nil;
	if ([self.modelClass respondsToSelector:@selector(propertyKeysForManagedObjectUniquing)]) {
		propertyKeys = [self.modelClass propertyKeysForManagedObjectUniquing];
	}
	
	NSPredicate *predicate = nil;
	for (NSString *propertyKey in propertyKeys) {
		NSString *managedObjectKey = [self managedObjectKeyForKey:propertyKey];
		if (managedObjectKey) {
			id transformedValue = [model valueForKeyPath:propertyKey];

			NSValueTransformer *attributeTransformer = [self entityAttributeTransformerForKey:propertyKey];
			if (attributeTransformer != nil) transformedValue = [attributeTransformer transformedValue:transformedValue];

			NSPredicate *subpredicate = [NSPredicate predicateWithFormat:@"%K == %@", managedObjectKey, transformedValue];
			predicate = [NSCompoundPredicate andPredicateWithSubpredicates:(predicate ? @[predicate, subpredicate] : @[subpredicate])];
		}
	}
	
	return predicate;
}