bevy/crates/bevy_reflect/src/reflect.rs
Gino Valente c2854a2a05
bevy_reflect: Deprecate PartialReflect::clone_value (#18284)
# Objective

#13432 added proper reflection-based cloning. This is a better method
than cloning via `clone_value` for reasons detailed in the description
of that PR. However, it may not be immediately apparent to users why one
should be used over the other, and what the gotchas of `clone_value`
are.

## Solution

This PR marks `PartialReflect::clone_value` as deprecated, with the
deprecation notice pointing users to `PartialReflect::reflect_clone`.
However, it also suggests using a new method introduced in this PR:
`PartialReflect::to_dynamic`.

`PartialReflect::to_dynamic` is essentially a renaming of
`PartialReflect::clone_value`. By naming it `to_dynamic`, we make it
very obvious that what's returned is a dynamic type. The one caveat to
this is that opaque types still use `reflect_clone` as they have no
corresponding dynamic type.

Along with changing the name, the method is now optional, and comes with
a default implementation that calls out to the respective reflection
subtrait method. This was done because there was really no reason to
require manual implementors provide a method that almost always calls
out to a known set of methods.

Lastly, to make this default implementation work, this PR also did a
similar thing with the `clone_dynamic ` methods on the reflection
subtraits. For example, `Struct::clone_dynamic` has been marked
deprecated and is superseded by `Struct::to_dynamic_struct`. This was
necessary to avoid the "multiple names in scope" issue.

### Open Questions

This PR maintains the original signature of `clone_value` on
`to_dynamic`. That is, it takes `&self` and returns `Box<dyn
PartialReflect>`.

However, in order for this to work, it introduces a panic if the value
is opaque and doesn't override the default `reflect_clone`
implementation.

One thing we could do to avoid the panic would be to make the conversion
fallible, either returning `Option<Box<dyn PartialReflect>>` or
`Result<Box<dyn PartialReflect>, ReflectCloneError>`.

This makes using the method a little more involved (i.e. users have to
either unwrap or handle the rare possibility of an error), but it would
set us up for a world where opaque types don't strictly need to be
`Clone`. Right now this bound is sort of implied by the fact that
`clone_value` is a required trait method, and the default behavior of
the macro is to use `Clone` for opaque types.

Alternatively, we could keep the signature but make the method required.
This maintains that implied bound where manual implementors must provide
some way of cloning the value (or YOLO it and just panic), but also
makes the API simpler to use.

Finally, we could just leave it with the panic. It's unlikely this would
occur in practice since our macro still requires `Clone` for opaque
types, and thus this would only ever be an issue if someone were to
manually implement `PartialReflect` without a valid `to_dynamic` or
`reflect_clone` method.

## Testing

You can test locally using the following command:

```
cargo test --package bevy_reflect --all-features
```

---

## Migration Guide

`PartialReflect::clone_value` is being deprecated. Instead, use
`PartialReflect::to_dynamic` if wanting to create a new dynamic instance
of the reflected value. Alternatively, use
`PartialReflect::reflect_clone` to attempt to create a true clone of the
underlying value.

Similarly, the following methods have been deprecated and should be
replaced with these alternatives:
- `Array::clone_dynamic` → `Array::to_dynamic_array`
- `Enum::clone_dynamic` → `Enum::to_dynamic_enum`
- `List::clone_dynamic` → `List::to_dynamic_list`
- `Map::clone_dynamic` → `Map::to_dynamic_map`
- `Set::clone_dynamic` → `Set::to_dynamic_set`
- `Struct::clone_dynamic` → `Struct::to_dynamic_struct`
- `Tuple::clone_dynamic` → `Tuple::to_dynamic_tuple`
- `TupleStruct::clone_dynamic` → `TupleStruct::to_dynamic_tuple_struct`
2025-03-14 19:33:57 +00:00

645 lines
25 KiB
Rust

use crate::{
array_debug, enum_debug, list_debug, map_debug, set_debug, struct_debug, tuple_debug,
tuple_struct_debug, DynamicTypePath, DynamicTyped, OpaqueInfo, ReflectCloneError, ReflectKind,
ReflectKindMismatchError, ReflectMut, ReflectOwned, ReflectRef, TypeInfo, TypePath, Typed,
};
use alloc::borrow::Cow;
use alloc::boxed::Box;
use alloc::string::ToString;
use core::{
any::{Any, TypeId},
fmt::Debug,
};
use thiserror::Error;
use crate::utility::NonGenericTypeInfoCell;
/// A enumeration of all error outcomes that might happen when running [`try_apply`](PartialReflect::try_apply).
#[derive(Error, Debug)]
pub enum ApplyError {
#[error("attempted to apply `{from_kind}` to `{to_kind}`")]
/// Attempted to apply the wrong [kind](ReflectKind) to a type, e.g. a struct to an enum.
MismatchedKinds {
from_kind: ReflectKind,
to_kind: ReflectKind,
},
#[error("enum variant `{variant_name}` doesn't have a field named `{field_name}`")]
/// Enum variant that we tried to apply to was missing a field.
MissingEnumField {
variant_name: Box<str>,
field_name: Box<str>,
},
#[error("`{from_type}` is not `{to_type}`")]
/// Tried to apply incompatible types.
MismatchedTypes {
from_type: Box<str>,
to_type: Box<str>,
},
#[error("attempted to apply type with {from_size} size to a type with {to_size} size")]
/// Attempted to apply to types with mismatched sizes, e.g. a [u8; 4] to [u8; 3].
DifferentSize { from_size: usize, to_size: usize },
#[error("variant with name `{variant_name}` does not exist on enum `{enum_name}`")]
/// The enum we tried to apply to didn't contain a variant with the give name.
UnknownVariant {
enum_name: Box<str>,
variant_name: Box<str>,
},
}
impl From<ReflectKindMismatchError> for ApplyError {
fn from(value: ReflectKindMismatchError) -> Self {
Self::MismatchedKinds {
from_kind: value.received,
to_kind: value.expected,
}
}
}
/// The foundational trait of [`bevy_reflect`], used for accessing and modifying data dynamically.
///
/// This is a supertrait of [`Reflect`],
/// meaning any type which implements `Reflect` implements `PartialReflect` by definition.
///
/// It's recommended to use [the derive macro for `Reflect`] rather than manually implementing this trait.
/// Doing so will automatically implement this trait as well as many other useful traits for reflection,
/// including one of the appropriate subtraits: [`Struct`], [`TupleStruct`] or [`Enum`].
///
/// See the [crate-level documentation] to see how this trait and its subtraits can be used.
///
/// [`bevy_reflect`]: crate
/// [the derive macro for `Reflect`]: bevy_reflect_derive::Reflect
/// [`Struct`]: crate::Struct
/// [`TupleStruct`]: crate::TupleStruct
/// [`Enum`]: crate::Enum
/// [crate-level documentation]: crate
#[diagnostic::on_unimplemented(
message = "`{Self}` does not implement `PartialReflect` so cannot be introspected",
note = "consider annotating `{Self}` with `#[derive(Reflect)]`"
)]
pub trait PartialReflect: DynamicTypePath + Send + Sync
where
// NB: we don't use `Self: Any` since for downcasting, `Reflect` should be used.
Self: 'static,
{
/// Returns the [`TypeInfo`] of the type _represented_ by this value.
///
/// For most types, this will simply return their own `TypeInfo`.
/// However, for dynamic types, such as [`DynamicStruct`] or [`DynamicList`],
/// this will return the type they represent
/// (or `None` if they don't represent any particular type).
///
/// This method is great if you have an instance of a type or a `dyn Reflect`,
/// and want to access its [`TypeInfo`]. However, if this method is to be called
/// frequently, consider using [`TypeRegistry::get_type_info`] as it can be more
/// performant for such use cases.
///
/// [`DynamicStruct`]: crate::DynamicStruct
/// [`DynamicList`]: crate::DynamicList
/// [`TypeRegistry::get_type_info`]: crate::TypeRegistry::get_type_info
fn get_represented_type_info(&self) -> Option<&'static TypeInfo>;
/// Casts this type to a boxed, reflected value.
///
/// This is useful for coercing trait objects.
fn into_partial_reflect(self: Box<Self>) -> Box<dyn PartialReflect>;
/// Casts this type to a reflected value.
///
/// This is useful for coercing trait objects.
fn as_partial_reflect(&self) -> &dyn PartialReflect;
/// Casts this type to a mutable, reflected value.
///
/// This is useful for coercing trait objects.
fn as_partial_reflect_mut(&mut self) -> &mut dyn PartialReflect;
/// Attempts to cast this type to a boxed, [fully-reflected] value.
///
/// [fully-reflected]: Reflect
fn try_into_reflect(self: Box<Self>) -> Result<Box<dyn Reflect>, Box<dyn PartialReflect>>;
/// Attempts to cast this type to a [fully-reflected] value.
///
/// [fully-reflected]: Reflect
fn try_as_reflect(&self) -> Option<&dyn Reflect>;
/// Attempts to cast this type to a mutable, [fully-reflected] value.
///
/// [fully-reflected]: Reflect
fn try_as_reflect_mut(&mut self) -> Option<&mut dyn Reflect>;
/// Applies a reflected value to this value.
///
/// If a type implements an [introspection subtrait], then the semantics of this
/// method are as follows:
/// - If `T` is a [`Struct`], then the value of each named field of `value` is
/// applied to the corresponding named field of `self`. Fields which are
/// not present in both structs are ignored.
/// - If `T` is a [`TupleStruct`] or [`Tuple`], then the value of each
/// numbered field is applied to the corresponding numbered field of
/// `self.` Fields which are not present in both values are ignored.
/// - If `T` is an [`Enum`], then the variant of `self` is `updated` to match
/// the variant of `value`. The corresponding fields of that variant are
/// applied from `value` onto `self`. Fields which are not present in both
/// values are ignored.
/// - If `T` is a [`List`] or [`Array`], then each element of `value` is applied
/// to the corresponding element of `self`. Up to `self.len()` items are applied,
/// and excess elements in `value` are appended to `self`.
/// - If `T` is a [`Map`], then for each key in `value`, the associated
/// value is applied to the value associated with the same key in `self`.
/// Keys which are not present in `self` are inserted.
/// - If `T` is none of these, then `value` is downcast to `T`, cloned, and
/// assigned to `self`.
///
/// Note that `Reflect` must be implemented manually for [`List`]s and
/// [`Map`]s in order to achieve the correct semantics, as derived
/// implementations will have the semantics for [`Struct`], [`TupleStruct`], [`Enum`]
/// or none of the above depending on the kind of type. For lists and maps, use the
/// [`list_apply`] and [`map_apply`] helper functions when implementing this method.
///
/// [introspection subtrait]: crate#the-introspection-subtraits
/// [`Struct`]: crate::Struct
/// [`TupleStruct`]: crate::TupleStruct
/// [`Tuple`]: crate::Tuple
/// [`Enum`]: crate::Enum
/// [`List`]: crate::List
/// [`Array`]: crate::Array
/// [`Map`]: crate::Map
/// [`list_apply`]: crate::list_apply
/// [`map_apply`]: crate::map_apply
///
/// # Panics
///
/// Derived implementations of this method will panic:
/// - If the type of `value` is not of the same kind as `T` (e.g. if `T` is
/// a `List`, while `value` is a `Struct`).
/// - If `T` is any complex type and the corresponding fields or elements of
/// `self` and `value` are not of the same type.
/// - If `T` is an opaque type and `self` cannot be downcast to `T`
fn apply(&mut self, value: &dyn PartialReflect) {
PartialReflect::try_apply(self, value).unwrap();
}
/// Tries to [`apply`](PartialReflect::apply) a reflected value to this value.
///
/// Functions the same as the [`apply`](PartialReflect::apply) function but returns an error instead of
/// panicking.
///
/// # Handling Errors
///
/// This function may leave `self` in a partially mutated state if a error was encountered on the way.
/// consider maintaining a cloned instance of this data you can switch to if a error is encountered.
fn try_apply(&mut self, value: &dyn PartialReflect) -> Result<(), ApplyError>;
/// Returns a zero-sized enumeration of "kinds" of type.
///
/// See [`ReflectKind`].
fn reflect_kind(&self) -> ReflectKind {
self.reflect_ref().kind()
}
/// Returns an immutable enumeration of "kinds" of type.
///
/// See [`ReflectRef`].
fn reflect_ref(&self) -> ReflectRef;
/// Returns a mutable enumeration of "kinds" of type.
///
/// See [`ReflectMut`].
fn reflect_mut(&mut self) -> ReflectMut;
/// Returns an owned enumeration of "kinds" of type.
///
/// See [`ReflectOwned`].
fn reflect_owned(self: Box<Self>) -> ReflectOwned;
/// Clones `Self` into its dynamic representation.
///
/// For value types or types marked with `#[reflect_value]`,
/// this will simply return a clone of `Self`.
///
/// Otherwise the associated dynamic type will be returned.
///
/// For example, a [`List`] type will invoke [`List::clone_dynamic`], returning [`DynamicList`].
/// A [`Struct`] type will invoke [`Struct::clone_dynamic`], returning [`DynamicStruct`].
/// And so on.
///
/// If the dynamic behavior is not desired, a concrete clone can be obtained using [`PartialReflect::reflect_clone`].
///
/// # Example
///
/// ```
/// # use bevy_reflect::{PartialReflect};
/// let value = (1, true, 3.14);
/// let cloned = value.clone_value();
/// assert!(cloned.is_dynamic())
/// ```
///
/// [`List`]: crate::List
/// [`List::clone_dynamic`]: crate::List::clone_dynamic
/// [`DynamicList`]: crate::DynamicList
/// [`Struct`]: crate::Struct
/// [`Struct::clone_dynamic`]: crate::Struct::clone_dynamic
/// [`DynamicStruct`]: crate::DynamicStruct
#[deprecated(
since = "0.16.0",
note = "to clone reflected values, prefer using `reflect_clone`. To convert reflected values to dynamic ones, use `to_dynamic`."
)]
fn clone_value(&self) -> Box<dyn PartialReflect> {
self.to_dynamic()
}
/// Converts this reflected value into its dynamic representation based on its [kind].
///
/// For example, a [`List`] type will internally invoke [`List::to_dynamic_list`], returning [`DynamicList`].
/// A [`Struct`] type will invoke [`Struct::to_dynamic_struct`], returning [`DynamicStruct`].
/// And so on.
///
/// If the [kind] is [opaque], then the value will attempt to be cloned directly via [`reflect_clone`],
/// since opaque types do not have any standard dynamic representation.
///
/// To attempt to clone the value directly such that it returns a concrete instance of this type,
/// use [`reflect_clone`].
///
/// # Panics
///
/// This method will panic if the [kind] is [opaque] and the call to [`reflect_clone`] fails.
///
/// # Example
///
/// ```
/// # use bevy_reflect::{PartialReflect};
/// let value = (1, true, 3.14);
/// let dynamic_value = value.to_dynamic();
/// assert!(dynamic_value.is_dynamic())
/// ```
///
/// [kind]: PartialReflect::reflect_kind
/// [`List`]: crate::List
/// [`List::to_dynamic_list`]: crate::List::to_dynamic_list
/// [`DynamicList`]: crate::DynamicList
/// [`Struct`]: crate::Struct
/// [`Struct::to_dynamic_struct`]: crate::Struct::to_dynamic_struct
/// [`DynamicStruct`]: crate::DynamicStruct
/// [opaque]: crate::ReflectKind::Opaque
/// [`reflect_clone`]: PartialReflect::reflect_clone
fn to_dynamic(&self) -> Box<dyn PartialReflect> {
match self.reflect_ref() {
ReflectRef::Struct(dyn_struct) => Box::new(dyn_struct.to_dynamic_struct()),
ReflectRef::TupleStruct(dyn_tuple_struct) => {
Box::new(dyn_tuple_struct.to_dynamic_tuple_struct())
}
ReflectRef::Tuple(dyn_tuple) => Box::new(dyn_tuple.to_dynamic_tuple()),
ReflectRef::List(dyn_list) => Box::new(dyn_list.to_dynamic_list()),
ReflectRef::Array(dyn_array) => Box::new(dyn_array.to_dynamic_array()),
ReflectRef::Map(dyn_map) => Box::new(dyn_map.to_dynamic_map()),
ReflectRef::Set(dyn_set) => Box::new(dyn_set.to_dynamic_set()),
ReflectRef::Enum(dyn_enum) => Box::new(dyn_enum.to_dynamic_enum()),
#[cfg(feature = "functions")]
ReflectRef::Function(dyn_function) => Box::new(dyn_function.to_dynamic_function()),
ReflectRef::Opaque(value) => value.reflect_clone().unwrap().into_partial_reflect(),
}
}
/// Attempts to clone `Self` using reflection.
///
/// Unlike [`to_dynamic`], which generally returns a dynamic representation of `Self`,
/// this method attempts create a clone of `Self` directly, if possible.
///
/// If the clone cannot be performed, an appropriate [`ReflectCloneError`] is returned.
///
/// # Example
///
/// ```
/// # use bevy_reflect::PartialReflect;
/// let value = (1, true, 3.14);
/// let cloned = value.reflect_clone().unwrap();
/// assert!(cloned.is::<(i32, bool, f64)>())
/// ```
///
/// [`to_dynamic`]: PartialReflect::to_dynamic
fn reflect_clone(&self) -> Result<Box<dyn Reflect>, ReflectCloneError> {
Err(ReflectCloneError::NotImplemented {
type_path: Cow::Owned(self.reflect_type_path().to_string()),
})
}
/// Returns a hash of the value (which includes the type).
///
/// If the underlying type does not support hashing, returns `None`.
fn reflect_hash(&self) -> Option<u64> {
None
}
/// Returns a "partial equality" comparison result.
///
/// If the underlying type does not support equality testing, returns `None`.
fn reflect_partial_eq(&self, _value: &dyn PartialReflect) -> Option<bool> {
None
}
/// Debug formatter for the value.
///
/// Any value that is not an implementor of other `Reflect` subtraits
/// (e.g. [`List`], [`Map`]), will default to the format: `"Reflect(type_path)"`,
/// where `type_path` is the [type path] of the underlying type.
///
/// [`List`]: crate::List
/// [`Map`]: crate::Map
/// [type path]: TypePath::type_path
fn debug(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
match self.reflect_ref() {
ReflectRef::Struct(dyn_struct) => struct_debug(dyn_struct, f),
ReflectRef::TupleStruct(dyn_tuple_struct) => tuple_struct_debug(dyn_tuple_struct, f),
ReflectRef::Tuple(dyn_tuple) => tuple_debug(dyn_tuple, f),
ReflectRef::List(dyn_list) => list_debug(dyn_list, f),
ReflectRef::Array(dyn_array) => array_debug(dyn_array, f),
ReflectRef::Map(dyn_map) => map_debug(dyn_map, f),
ReflectRef::Set(dyn_set) => set_debug(dyn_set, f),
ReflectRef::Enum(dyn_enum) => enum_debug(dyn_enum, f),
#[cfg(feature = "functions")]
ReflectRef::Function(dyn_function) => dyn_function.fmt(f),
ReflectRef::Opaque(_) => write!(f, "Reflect({})", self.reflect_type_path()),
}
}
/// Indicates whether or not this type is a _dynamic_ type.
///
/// Dynamic types include the ones built-in to this [crate],
/// such as [`DynamicStruct`], [`DynamicList`], and [`DynamicTuple`].
/// However, they may be custom types used as proxies for other types
/// or to facilitate scripting capabilities.
///
/// By default, this method will return `false`.
///
/// [`DynamicStruct`]: crate::DynamicStruct
/// [`DynamicList`]: crate::DynamicList
/// [`DynamicTuple`]: crate::DynamicTuple
fn is_dynamic(&self) -> bool {
false
}
}
/// A core trait of [`bevy_reflect`], used for downcasting to concrete types.
///
/// This is a subtrait of [`PartialReflect`],
/// meaning any type which implements `Reflect` implements `PartialReflect` by definition.
///
/// It's recommended to use [the derive macro] rather than manually implementing this trait.
/// Doing so will automatically implement this trait, [`PartialReflect`], and many other useful traits for reflection,
/// including one of the appropriate subtraits: [`Struct`], [`TupleStruct`] or [`Enum`].
///
/// If you need to use this trait as a generic bound along with other reflection traits,
/// for your convenience, consider using [`Reflectable`] instead.
///
/// See the [crate-level documentation] to see how this trait can be used.
///
/// [`bevy_reflect`]: crate
/// [the derive macro]: bevy_reflect_derive::Reflect
/// [`Struct`]: crate::Struct
/// [`TupleStruct`]: crate::TupleStruct
/// [`Enum`]: crate::Enum
/// [`Reflectable`]: crate::Reflectable
/// [crate-level documentation]: crate
#[diagnostic::on_unimplemented(
message = "`{Self}` does not implement `Reflect` so cannot be fully reflected",
note = "consider annotating `{Self}` with `#[derive(Reflect)]`"
)]
pub trait Reflect: PartialReflect + DynamicTyped + Any {
/// Returns the value as a [`Box<dyn Any>`][core::any::Any].
///
/// For remote wrapper types, this will return the remote type instead.
fn into_any(self: Box<Self>) -> Box<dyn Any>;
/// Returns the value as a [`&dyn Any`][core::any::Any].
///
/// For remote wrapper types, this will return the remote type instead.
fn as_any(&self) -> &dyn Any;
/// Returns the value as a [`&mut dyn Any`][core::any::Any].
///
/// For remote wrapper types, this will return the remote type instead.
fn as_any_mut(&mut self) -> &mut dyn Any;
/// Casts this type to a boxed, fully-reflected value.
fn into_reflect(self: Box<Self>) -> Box<dyn Reflect>;
/// Casts this type to a fully-reflected value.
fn as_reflect(&self) -> &dyn Reflect;
/// Casts this type to a mutable, fully-reflected value.
fn as_reflect_mut(&mut self) -> &mut dyn Reflect;
/// Performs a type-checked assignment of a reflected value to this value.
///
/// If `value` does not contain a value of type `T`, returns an `Err`
/// containing the trait object.
fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>>;
}
impl dyn PartialReflect {
/// Returns `true` if the underlying value represents a value of type `T`, or `false`
/// otherwise.
///
/// Read `is` for more information on underlying values and represented types.
#[inline]
pub fn represents<T: Reflect + TypePath>(&self) -> bool {
self.get_represented_type_info()
.is_some_and(|t| t.type_path() == T::type_path())
}
/// Downcasts the value to type `T`, consuming the trait object.
///
/// If the underlying value does not implement [`Reflect`]
/// or is not of type `T`, returns `Err(self)`.
///
/// For remote types, `T` should be the type itself rather than the wrapper type.
pub fn try_downcast<T: Any>(
self: Box<dyn PartialReflect>,
) -> Result<Box<T>, Box<dyn PartialReflect>> {
self.try_into_reflect()?
.downcast()
.map_err(PartialReflect::into_partial_reflect)
}
/// Downcasts the value to type `T`, unboxing and consuming the trait object.
///
/// If the underlying value does not implement [`Reflect`]
/// or is not of type `T`, returns `Err(self)`.
///
/// For remote types, `T` should be the type itself rather than the wrapper type.
pub fn try_take<T: Any>(self: Box<dyn PartialReflect>) -> Result<T, Box<dyn PartialReflect>> {
self.try_downcast().map(|value| *value)
}
/// Downcasts the value to type `T` by reference.
///
/// If the underlying value does not implement [`Reflect`]
/// or is not of type `T`, returns [`None`].
///
/// For remote types, `T` should be the type itself rather than the wrapper type.
pub fn try_downcast_ref<T: Any>(&self) -> Option<&T> {
self.try_as_reflect()?.downcast_ref()
}
/// Downcasts the value to type `T` by mutable reference.
///
/// If the underlying value does not implement [`Reflect`]
/// or is not of type `T`, returns [`None`].
///
/// For remote types, `T` should be the type itself rather than the wrapper type.
pub fn try_downcast_mut<T: Any>(&mut self) -> Option<&mut T> {
self.try_as_reflect_mut()?.downcast_mut()
}
}
impl Debug for dyn PartialReflect {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
self.debug(f)
}
}
// The following implementation never actually shadows the concrete TypePath implementation.
// See the comment on `dyn Reflect`'s `TypePath` implementation.
impl TypePath for dyn PartialReflect {
fn type_path() -> &'static str {
"dyn bevy_reflect::PartialReflect"
}
fn short_type_path() -> &'static str {
"dyn PartialReflect"
}
}
#[deny(rustdoc::broken_intra_doc_links)]
impl dyn Reflect {
/// Downcasts the value to type `T`, consuming the trait object.
///
/// If the underlying value is not of type `T`, returns `Err(self)`.
///
/// For remote types, `T` should be the type itself rather than the wrapper type.
pub fn downcast<T: Any>(self: Box<dyn Reflect>) -> Result<Box<T>, Box<dyn Reflect>> {
if self.is::<T>() {
Ok(self.into_any().downcast().unwrap())
} else {
Err(self)
}
}
/// Downcasts the value to type `T`, unboxing and consuming the trait object.
///
/// If the underlying value is not of type `T`, returns `Err(self)`.
///
/// For remote types, `T` should be the type itself rather than the wrapper type.
pub fn take<T: Any>(self: Box<dyn Reflect>) -> Result<T, Box<dyn Reflect>> {
self.downcast::<T>().map(|value| *value)
}
/// Returns `true` if the underlying value is of type `T`, or `false`
/// otherwise.
///
/// The underlying value is the concrete type that is stored in this `dyn` object;
/// it can be downcasted to. In the case that this underlying value "represents"
/// a different type, like the Dynamic\*\*\* types do, you can call `represents`
/// to determine what type they represent. Represented types cannot be downcasted
/// to, but you can use [`FromReflect`] to create a value of the represented type from them.
///
/// For remote types, `T` should be the type itself rather than the wrapper type.
///
/// [`FromReflect`]: crate::FromReflect
#[inline]
pub fn is<T: Any>(&self) -> bool {
self.as_any().type_id() == TypeId::of::<T>()
}
/// Downcasts the value to type `T` by reference.
///
/// If the underlying value is not of type `T`, returns `None`.
///
/// For remote types, `T` should be the type itself rather than the wrapper type.
#[inline]
pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
self.as_any().downcast_ref::<T>()
}
/// Downcasts the value to type `T` by mutable reference.
///
/// If the underlying value is not of type `T`, returns `None`.
///
/// For remote types, `T` should be the type itself rather than the wrapper type.
#[inline]
pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T> {
self.as_any_mut().downcast_mut::<T>()
}
}
impl Debug for dyn Reflect {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
self.debug(f)
}
}
impl Typed for dyn Reflect {
fn type_info() -> &'static TypeInfo {
static CELL: NonGenericTypeInfoCell = NonGenericTypeInfoCell::new();
CELL.get_or_set(|| TypeInfo::Opaque(OpaqueInfo::new::<Self>()))
}
}
// The following implementation never actually shadows the concrete `TypePath` implementation.
// See this playground (https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=589064053f27bc100d90da89c6a860aa).
impl TypePath for dyn Reflect {
fn type_path() -> &'static str {
"dyn bevy_reflect::Reflect"
}
fn short_type_path() -> &'static str {
"dyn Reflect"
}
}
macro_rules! impl_full_reflect {
($(<$($id:ident),* $(,)?>)? for $ty:ty $(where $($tt:tt)*)?) => {
impl $(<$($id),*>)? $crate::Reflect for $ty $(where $($tt)*)? {
fn into_any(self: Box<Self>) -> Box<dyn ::core::any::Any> {
self
}
fn as_any(&self) -> &dyn ::core::any::Any {
self
}
fn as_any_mut(&mut self) -> &mut dyn ::core::any::Any {
self
}
fn into_reflect(self: Box<Self>) -> Box<dyn $crate::Reflect> {
self
}
fn as_reflect(&self) -> &dyn $crate::Reflect {
self
}
fn as_reflect_mut(&mut self) -> &mut dyn $crate::Reflect {
self
}
fn set(
&mut self,
value: Box<dyn $crate::Reflect>,
) -> Result<(), Box<dyn $crate::Reflect>> {
*self = <dyn $crate::Reflect>::take(value)?;
Ok(())
}
}
};
}
pub(crate) use impl_full_reflect;