Originally posted by **ozaner** December 25, 2022
```dart
@jsonSerializable
class ComposableCar {
@JsonProperty(name: 'leftWheel/tire/thickness')
final int thicknessLeft;
@JsonProperty(name: 'rightWheel/tire/thickness')
final int thicknessRight;
@JsonProperty(name: 'rightWheel/tire/color')
final String? tireRightColor;
const ComposableCar(this.thicknessLeft, this.thicknessRight, this.tireRightColor);
}
```
If we run the `copyWith` method on this:
```dart
var newCar = JsonMapper.copyWith(car, {'rightWheel': {'tire': {'thickness': 32}}})
```
it doesn't copy `tireRightColor` when creating the new car.
Discussed in https://github.com/k-paxian/dart-json-mapper/discussions/208