mirror of
https://github.com/bevyengine/bevy
synced 2024-11-10 07:04:33 +00:00
e512cb602c
# Objective
There are times when we might know the type of a `TypeInfo` ahead of
time. Or we may have already checked it one way or another.
In such cases, it's a bit cumbersome to have to pattern match every time
we want to access the nested info:
```rust
if let TypeInfo::List(info) = <Vec<i32>>::type_info() {
// ...
} else {
panic!("expected list info");
}
```
Ideally, there would be a way to simply perform the cast down to
`ListInfo` since we already know it will succeed.
Or even if we don't, perhaps we just want a cleaner way of exiting a
function early (i.e. with the `?` operator).
## Solution
Taking a bit from
[`mirror-mirror`](https://docs.rs/mirror-mirror/latest/mirror_mirror/struct.TypeDescriptor.html#implementations),
`TypeInfo` now has methods for attempting a cast into the variant's info
type.
```rust
let info = <Vec<i32>>::type_info().as_list().unwrap();
// ...
```
These new conversion methods return a `Result` where the error type is a
new `TypeInfoError` enum.
A `Result` was chosen as the return type over `Option` because if we do
choose to `unwrap` it, the error message will give us some indication of
what went wrong. In other words, it can truly replace those instances
where we were panicking in the `else` case.
### Open Questions
1. Should the error types instead be a struct? I chose an enum for
future-proofing, but right now it only has one error state.
Alternatively, we could make it a reflect-wide casting error so it could
be used for similar methods on `ReflectRef` and friends.
2. I was going to do it in a separate PR but should I just go ahead and
add similar methods to `ReflectRef`, `ReflectMut`, and `ReflectOwned`? 🤔
3. Should we name these `try_as_***` instead of `as_***` since they
return a `Result`?
## Testing
You can test locally by running:
```
cargo test --package bevy_reflect
```
---
## Changelog
### Added
- `TypeInfoError` enum
- `TypeInfo::kind` method
- `TypeInfo::as_struct` method
- `TypeInfo::as_tuple_struct` method
- `TypeInfo::as_tuple` method
- `TypeInfo::as_list` method
- `TypeInfo::as_array` method
- `TypeInfo::as_map` method
- `TypeInfo::as_enum` method
- `TypeInfo::as_value` method
- `VariantInfoError` enum
- `VariantInfo::variant_type` method
- `VariantInfo::as_unit_variant` method
- `VariantInfo::as_tuple_variant` method
- `VariantInfo::as_struct_variant` method
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|---|---|---|
| .. | ||
| bevy_a11y | ||
| bevy_animation | ||
| bevy_app | ||
| bevy_asset | ||
| bevy_audio | ||
| bevy_color | ||
| bevy_core | ||
| bevy_core_pipeline | ||
| bevy_derive | ||
| bevy_dev_tools | ||
| bevy_diagnostic | ||
| bevy_dylib | ||
| bevy_dynamic_plugin | ||
| bevy_ecs | ||
| bevy_encase_derive | ||
| bevy_gilrs | ||
| bevy_gizmos | ||
| bevy_gltf | ||
| bevy_hierarchy | ||
| bevy_input | ||
| bevy_internal | ||
| bevy_log | ||
| bevy_macro_utils | ||
| bevy_math | ||
| bevy_mikktspace | ||
| bevy_pbr | ||
| bevy_picking | ||
| bevy_ptr | ||
| bevy_reflect | ||
| bevy_render | ||
| bevy_scene | ||
| bevy_sprite | ||
| bevy_state | ||
| bevy_tasks | ||
| bevy_text | ||
| bevy_time | ||
| bevy_transform | ||
| bevy_ui | ||
| bevy_utils | ||
| bevy_window | ||
| bevy_winit | ||