return association.Error
		}

		// set old associations's foreign key to null
		switch rel.Type {
		case schema.BelongsTo:
			if len(values) == 0 {
				updateMap := map[string]interface{}{}
				switch reflectValue.Kind() {
				case reflect.Slice, reflect.Array:
					for i := 0; i < reflectValue.Len(); i++ {