# Objective
- Fixes#17411
## Solution
- Deprecated `Component::register_component_hooks`
- Added individual methods for each hook which return `None` if the hook
is unused.
## Testing
- CI
---
## Migration Guide
`Component::register_component_hooks` is now deprecated and will be
removed in a future release. When implementing `Component` manually,
also implement the respective hook methods on `Component`.
```rust
// Before
impl Component for Foo {
// snip
fn register_component_hooks(hooks: &mut ComponentHooks) {
hooks.on_add(foo_on_add);
}
}
// After
impl Component for Foo {
// snip
fn on_add() -> Option<ComponentHook> {
Some(foo_on_add)
}
}
```
## Notes
I've chosen to deprecate `Component::register_component_hooks` rather
than outright remove it to ease the migration guide. While it is in a
state of deprecation, it must be used by
`Components::register_component_internal` to ensure users who haven't
migrated to the new hook definition scheme aren't left behind. For users
of the new scheme, a default implementation of
`Component::register_component_hooks` is provided which forwards the new
individual hook implementations.
Personally, I think this is a cleaner API to work with, and would allow
the documentation for hooks to exist on the respective `Component`
methods (e.g., documentation for `OnAdd` can exist on
`Component::on_add`). Ideally, `Component::on_add` would be the hook
itself rather than a getter for the hook, but it is the only way to
early-out for a no-op hook, which is important for performance.
## Migration Guide
`Component::register_component_hooks` has been deprecated. If you are
manually implementing the `Component` trait and registering hooks there,
use the individual methods such as `on_add` instead for increased
clarity.
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