# Objective
`Scene` and `DynamicScene` work with `InstanceInfo` at different levels
of abstraction
- `Scene::write_to_world_with` returns an `InstanceInfo` whereas
`DynamicScene::write_to_world_with` returns `()`. Instances are created
one level higher at the `SceneSpawner` API level.
- `DynamicScene::write_to_world_with` takes the `entity_map` as an
argument whereas the `Scene` version is less flexible and creates a new
one for you. No reason this needs to be the case.
## Solution
I propose changing `Scene::write_to_world_with` to match the API we have
for `DynamicScene`. Returning the `InstanceInfo` as we do today just
seems like a leaky abstraction - it's only used in
`spawn_sync_internal`. Being able to pass in an entity_map gives you
more flexibility with how you write entities to a world.
This also moves `InstanceInfo` out of `Scene` which is cleaner
conceptually. If someone wants to work with instances then they should
work with `SceneSpawner` - I see `write_to_world_with` as a lower-level
API to be used with exclusive world access.
## Testing
Code is just shifting things around.
## Changelog
Changed `Scene::write_to_world_with` to take `entity_map` as an argument
and no longer return an `InstanceInfo`
## Migration Guide
`Scene::write_to_world_with` no longer returns an `InstanceInfo`.
Before
```rust
scene.write_to_world_with(world, ®istry)
```
After
```rust
let mut entity_map = EntityHashMap::default();
scene.write_to_world_with(world, &mut entity_map, ®istry)
```
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