bevy_reflect/
list.rs

1use alloc::{boxed::Box, vec::Vec};
2use core::{
3    any::Any,
4    fmt::{Debug, Formatter},
5    hash::{Hash, Hasher},
6};
7
8use bevy_reflect_derive::impl_type_path;
9
10use crate::generics::impl_generic_info_methods;
11use crate::{
12    type_info::impl_type_methods, utility::reflect_hasher, ApplyError, FromReflect, Generics,
13    MaybeTyped, PartialReflect, Reflect, ReflectKind, ReflectMut, ReflectOwned, ReflectRef, Type,
14    TypeInfo, TypePath,
15};
16
17/// A trait used to power [list-like] operations via [reflection].
18///
19/// This corresponds to types, like [`Vec`], which contain an ordered sequence
20/// of elements that implement [`Reflect`].
21///
22/// Unlike the [`Array`](crate::Array) trait, implementors of this trait are not expected to
23/// maintain a constant length.
24/// Methods like [insertion](List::insert) and [removal](List::remove) explicitly allow for their
25/// internal size to change.
26///
27/// [`push`](List::push) and [`pop`](List::pop) have default implementations,
28/// however it will generally be more performant to implement them manually
29/// as the default implementation uses a very naive approach to find the correct position.
30///
31/// This trait expects its elements to be ordered linearly from front to back.
32/// The _front_ element starts at index 0 with the _back_ element ending at the largest index.
33/// This contract above should be upheld by any manual implementors.
34///
35/// Due to the [type-erasing] nature of the reflection API as a whole,
36/// this trait does not make any guarantees that the implementor's elements
37/// are homogeneous (i.e. all the same type).
38///
39/// # Example
40///
41/// ```
42/// use bevy_reflect::{PartialReflect, Reflect, List};
43///
44/// let foo: &mut dyn List = &mut vec![123_u32, 456_u32, 789_u32];
45/// assert_eq!(foo.len(), 3);
46///
47/// let last_field: Box<dyn PartialReflect> = foo.pop().unwrap();
48/// assert_eq!(last_field.try_downcast_ref::<u32>(), Some(&789));
49/// ```
50///
51/// [list-like]: https://doc.rust-lang.org/book/ch08-01-vectors.html
52/// [reflection]: crate
53/// [type-erasing]: https://doc.rust-lang.org/book/ch17-02-trait-objects.html
54pub trait List: PartialReflect {
55    /// Returns a reference to the element at `index`, or `None` if out of bounds.
56    fn get(&self, index: usize) -> Option<&dyn PartialReflect>;
57
58    /// Returns a mutable reference to the element at `index`, or `None` if out of bounds.
59    fn get_mut(&mut self, index: usize) -> Option<&mut dyn PartialReflect>;
60
61    /// Inserts an element at position `index` within the list,
62    /// shifting all elements after it towards the back of the list.
63    ///
64    /// # Panics
65    /// Panics if `index > len`.
66    fn insert(&mut self, index: usize, element: Box<dyn PartialReflect>);
67
68    /// Removes and returns the element at position `index` within the list,
69    /// shifting all elements before it towards the front of the list.
70    ///
71    /// # Panics
72    /// Panics if `index` is out of bounds.
73    fn remove(&mut self, index: usize) -> Box<dyn PartialReflect>;
74
75    /// Appends an element to the _back_ of the list.
76    fn push(&mut self, value: Box<dyn PartialReflect>) {
77        self.insert(self.len(), value);
78    }
79
80    /// Removes the _back_ element from the list and returns it, or [`None`] if it is empty.
81    fn pop(&mut self) -> Option<Box<dyn PartialReflect>> {
82        if self.is_empty() {
83            None
84        } else {
85            Some(self.remove(self.len() - 1))
86        }
87    }
88
89    /// Returns the number of elements in the list.
90    fn len(&self) -> usize;
91
92    /// Returns `true` if the collection contains no elements.
93    fn is_empty(&self) -> bool {
94        self.len() == 0
95    }
96
97    /// Returns an iterator over the list.
98    fn iter(&self) -> ListIter;
99
100    /// Drain the elements of this list to get a vector of owned values.
101    ///
102    /// After calling this function, `self` will be empty. The order of items in the returned
103    /// [`Vec`] will match the order of items in `self`.
104    fn drain(&mut self) -> Vec<Box<dyn PartialReflect>>;
105
106    /// Clones the list, producing a [`DynamicList`].
107    #[deprecated(since = "0.16.0", note = "use `to_dynamic_list` instead")]
108    fn clone_dynamic(&self) -> DynamicList {
109        self.to_dynamic_list()
110    }
111
112    /// Creates a new [`DynamicList`] from this list.
113    fn to_dynamic_list(&self) -> DynamicList {
114        DynamicList {
115            represented_type: self.get_represented_type_info(),
116            values: self.iter().map(PartialReflect::to_dynamic).collect(),
117        }
118    }
119
120    /// Will return `None` if [`TypeInfo`] is not available.
121    fn get_represented_list_info(&self) -> Option<&'static ListInfo> {
122        self.get_represented_type_info()?.as_list().ok()
123    }
124}
125
126/// A container for compile-time list info.
127#[derive(Clone, Debug)]
128pub struct ListInfo {
129    ty: Type,
130    generics: Generics,
131    item_info: fn() -> Option<&'static TypeInfo>,
132    item_ty: Type,
133    #[cfg(feature = "documentation")]
134    docs: Option<&'static str>,
135}
136
137impl ListInfo {
138    /// Create a new [`ListInfo`].
139    pub fn new<TList: List + TypePath, TItem: FromReflect + MaybeTyped + TypePath>() -> Self {
140        Self {
141            ty: Type::of::<TList>(),
142            generics: Generics::new(),
143            item_info: TItem::maybe_type_info,
144            item_ty: Type::of::<TItem>(),
145            #[cfg(feature = "documentation")]
146            docs: None,
147        }
148    }
149
150    /// Sets the docstring for this list.
151    #[cfg(feature = "documentation")]
152    pub fn with_docs(self, docs: Option<&'static str>) -> Self {
153        Self { docs, ..self }
154    }
155
156    impl_type_methods!(ty);
157
158    /// The [`TypeInfo`] of the list item.
159    ///
160    /// Returns `None` if the list item does not contain static type information,
161    /// such as for dynamic types.
162    pub fn item_info(&self) -> Option<&'static TypeInfo> {
163        (self.item_info)()
164    }
165
166    /// The [type] of the list item.
167    ///
168    /// [type]: Type
169    pub fn item_ty(&self) -> Type {
170        self.item_ty
171    }
172
173    /// The docstring of this list, if any.
174    #[cfg(feature = "documentation")]
175    pub fn docs(&self) -> Option<&'static str> {
176        self.docs
177    }
178
179    impl_generic_info_methods!(generics);
180}
181
182/// A list of reflected values.
183#[derive(Default)]
184pub struct DynamicList {
185    represented_type: Option<&'static TypeInfo>,
186    values: Vec<Box<dyn PartialReflect>>,
187}
188
189impl DynamicList {
190    /// Sets the [type] to be represented by this `DynamicList`.
191    /// # Panics
192    ///
193    /// Panics if the given [type] is not a [`TypeInfo::List`].
194    ///
195    /// [type]: TypeInfo
196    pub fn set_represented_type(&mut self, represented_type: Option<&'static TypeInfo>) {
197        if let Some(represented_type) = represented_type {
198            assert!(
199                matches!(represented_type, TypeInfo::List(_)),
200                "expected TypeInfo::List but received: {:?}",
201                represented_type
202            );
203        }
204
205        self.represented_type = represented_type;
206    }
207
208    /// Appends a typed value to the list.
209    pub fn push<T: PartialReflect>(&mut self, value: T) {
210        self.values.push(Box::new(value));
211    }
212
213    /// Appends a [`Reflect`] trait object to the list.
214    pub fn push_box(&mut self, value: Box<dyn PartialReflect>) {
215        self.values.push(value);
216    }
217}
218
219impl List for DynamicList {
220    fn get(&self, index: usize) -> Option<&dyn PartialReflect> {
221        self.values.get(index).map(|value| &**value)
222    }
223
224    fn get_mut(&mut self, index: usize) -> Option<&mut dyn PartialReflect> {
225        self.values.get_mut(index).map(|value| &mut **value)
226    }
227
228    fn insert(&mut self, index: usize, element: Box<dyn PartialReflect>) {
229        self.values.insert(index, element);
230    }
231
232    fn remove(&mut self, index: usize) -> Box<dyn PartialReflect> {
233        self.values.remove(index)
234    }
235
236    fn push(&mut self, value: Box<dyn PartialReflect>) {
237        DynamicList::push_box(self, value);
238    }
239
240    fn pop(&mut self) -> Option<Box<dyn PartialReflect>> {
241        self.values.pop()
242    }
243
244    fn len(&self) -> usize {
245        self.values.len()
246    }
247
248    fn iter(&self) -> ListIter {
249        ListIter::new(self)
250    }
251
252    fn drain(&mut self) -> Vec<Box<dyn PartialReflect>> {
253        self.values.drain(..).collect()
254    }
255}
256
257impl PartialReflect for DynamicList {
258    #[inline]
259    fn get_represented_type_info(&self) -> Option<&'static TypeInfo> {
260        self.represented_type
261    }
262
263    #[inline]
264    fn into_partial_reflect(self: Box<Self>) -> Box<dyn PartialReflect> {
265        self
266    }
267
268    #[inline]
269    fn as_partial_reflect(&self) -> &dyn PartialReflect {
270        self
271    }
272
273    #[inline]
274    fn as_partial_reflect_mut(&mut self) -> &mut dyn PartialReflect {
275        self
276    }
277
278    fn try_into_reflect(self: Box<Self>) -> Result<Box<dyn Reflect>, Box<dyn PartialReflect>> {
279        Err(self)
280    }
281
282    fn try_as_reflect(&self) -> Option<&dyn Reflect> {
283        None
284    }
285
286    fn try_as_reflect_mut(&mut self) -> Option<&mut dyn Reflect> {
287        None
288    }
289
290    fn apply(&mut self, value: &dyn PartialReflect) {
291        list_apply(self, value);
292    }
293
294    fn try_apply(&mut self, value: &dyn PartialReflect) -> Result<(), ApplyError> {
295        list_try_apply(self, value)
296    }
297
298    #[inline]
299    fn reflect_kind(&self) -> ReflectKind {
300        ReflectKind::List
301    }
302
303    #[inline]
304    fn reflect_ref(&self) -> ReflectRef {
305        ReflectRef::List(self)
306    }
307
308    #[inline]
309    fn reflect_mut(&mut self) -> ReflectMut {
310        ReflectMut::List(self)
311    }
312
313    #[inline]
314    fn reflect_owned(self: Box<Self>) -> ReflectOwned {
315        ReflectOwned::List(self)
316    }
317
318    #[inline]
319    fn reflect_hash(&self) -> Option<u64> {
320        list_hash(self)
321    }
322
323    fn reflect_partial_eq(&self, value: &dyn PartialReflect) -> Option<bool> {
324        list_partial_eq(self, value)
325    }
326
327    fn debug(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
328        write!(f, "DynamicList(")?;
329        list_debug(self, f)?;
330        write!(f, ")")
331    }
332
333    #[inline]
334    fn is_dynamic(&self) -> bool {
335        true
336    }
337}
338
339impl_type_path!((in bevy_reflect) DynamicList);
340
341impl Debug for DynamicList {
342    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
343        self.debug(f)
344    }
345}
346
347impl FromIterator<Box<dyn PartialReflect>> for DynamicList {
348    fn from_iter<I: IntoIterator<Item = Box<dyn PartialReflect>>>(values: I) -> Self {
349        Self {
350            represented_type: None,
351            values: values.into_iter().collect(),
352        }
353    }
354}
355
356impl<T: PartialReflect> FromIterator<T> for DynamicList {
357    fn from_iter<I: IntoIterator<Item = T>>(values: I) -> Self {
358        values
359            .into_iter()
360            .map(|field| Box::new(field).into_partial_reflect())
361            .collect()
362    }
363}
364
365impl IntoIterator for DynamicList {
366    type Item = Box<dyn PartialReflect>;
367    type IntoIter = alloc::vec::IntoIter<Self::Item>;
368
369    fn into_iter(self) -> Self::IntoIter {
370        self.values.into_iter()
371    }
372}
373
374impl<'a> IntoIterator for &'a DynamicList {
375    type Item = &'a dyn PartialReflect;
376    type IntoIter = ListIter<'a>;
377
378    fn into_iter(self) -> Self::IntoIter {
379        self.iter()
380    }
381}
382
383/// An iterator over an [`List`].
384pub struct ListIter<'a> {
385    list: &'a dyn List,
386    index: usize,
387}
388
389impl ListIter<'_> {
390    /// Creates a new [`ListIter`].
391    #[inline]
392    pub const fn new(list: &dyn List) -> ListIter {
393        ListIter { list, index: 0 }
394    }
395}
396
397impl<'a> Iterator for ListIter<'a> {
398    type Item = &'a dyn PartialReflect;
399
400    #[inline]
401    fn next(&mut self) -> Option<Self::Item> {
402        let value = self.list.get(self.index);
403        self.index += value.is_some() as usize;
404        value
405    }
406
407    #[inline]
408    fn size_hint(&self) -> (usize, Option<usize>) {
409        let size = self.list.len();
410        (size, Some(size))
411    }
412}
413
414impl ExactSizeIterator for ListIter<'_> {}
415
416/// Returns the `u64` hash of the given [list](List).
417#[inline]
418pub fn list_hash<L: List>(list: &L) -> Option<u64> {
419    let mut hasher = reflect_hasher();
420    Any::type_id(list).hash(&mut hasher);
421    list.len().hash(&mut hasher);
422    for value in list.iter() {
423        hasher.write_u64(value.reflect_hash()?);
424    }
425    Some(hasher.finish())
426}
427
428/// Applies the elements of `b` to the corresponding elements of `a`.
429///
430/// If the length of `b` is greater than that of `a`, the excess elements of `b`
431/// are cloned and appended to `a`.
432///
433/// # Panics
434///
435/// This function panics if `b` is not a list.
436#[inline]
437pub fn list_apply<L: List>(a: &mut L, b: &dyn PartialReflect) {
438    if let Err(err) = list_try_apply(a, b) {
439        panic!("{err}");
440    }
441}
442
443/// Tries to apply the elements of `b` to the corresponding elements of `a` and
444/// returns a Result.
445///
446/// If the length of `b` is greater than that of `a`, the excess elements of `b`
447/// are cloned and appended to `a`.
448///
449/// # Errors
450///
451/// This function returns an [`ApplyError::MismatchedKinds`] if `b` is not a list or if
452/// applying elements to each other fails.
453#[inline]
454pub fn list_try_apply<L: List>(a: &mut L, b: &dyn PartialReflect) -> Result<(), ApplyError> {
455    let list_value = b.reflect_ref().as_list()?;
456
457    for (i, value) in list_value.iter().enumerate() {
458        if i < a.len() {
459            if let Some(v) = a.get_mut(i) {
460                v.try_apply(value)?;
461            }
462        } else {
463            List::push(a, value.to_dynamic());
464        }
465    }
466
467    Ok(())
468}
469
470/// Compares a [`List`] with a [`Reflect`] value.
471///
472/// Returns true if and only if all of the following are true:
473/// - `b` is a list;
474/// - `b` is the same length as `a`;
475/// - [`PartialReflect::reflect_partial_eq`] returns `Some(true)` for pairwise elements of `a` and `b`.
476///
477/// Returns [`None`] if the comparison couldn't even be performed.
478#[inline]
479pub fn list_partial_eq<L: List + ?Sized>(a: &L, b: &dyn PartialReflect) -> Option<bool> {
480    let ReflectRef::List(list) = b.reflect_ref() else {
481        return Some(false);
482    };
483
484    if a.len() != list.len() {
485        return Some(false);
486    }
487
488    for (a_value, b_value) in a.iter().zip(list.iter()) {
489        let eq_result = a_value.reflect_partial_eq(b_value);
490        if let failed @ (Some(false) | None) = eq_result {
491            return failed;
492        }
493    }
494
495    Some(true)
496}
497
498/// The default debug formatter for [`List`] types.
499///
500/// # Example
501/// ```
502/// use bevy_reflect::Reflect;
503///
504/// let my_list: &dyn Reflect = &vec![1, 2, 3];
505/// println!("{:#?}", my_list);
506///
507/// // Output:
508///
509/// // [
510/// //   1,
511/// //   2,
512/// //   3,
513/// // ]
514/// ```
515#[inline]
516pub fn list_debug(dyn_list: &dyn List, f: &mut Formatter<'_>) -> core::fmt::Result {
517    let mut debug = f.debug_list();
518    for item in dyn_list.iter() {
519        debug.entry(&item as &dyn Debug);
520    }
521    debug.finish()
522}
523
524#[cfg(test)]
525mod tests {
526    use super::DynamicList;
527    use crate::Reflect;
528    use alloc::{boxed::Box, vec};
529    use core::assert_eq;
530
531    #[test]
532    fn test_into_iter() {
533        let mut list = DynamicList::default();
534        list.push(0usize);
535        list.push(1usize);
536        list.push(2usize);
537        let items = list.into_iter();
538        for (index, item) in items.into_iter().enumerate() {
539            let value = item
540                .try_take::<usize>()
541                .expect("couldn't downcast to usize");
542            assert_eq!(index, value);
543        }
544    }
545
546    #[test]
547    fn next_index_increment() {
548        const SIZE: usize = if cfg!(debug_assertions) {
549            4
550        } else {
551            // If compiled in release mode, verify we dont overflow
552            usize::MAX
553        };
554        let b = Box::new(vec![(); SIZE]).into_reflect();
555
556        let list = b.reflect_ref().as_list().unwrap();
557
558        let mut iter = list.iter();
559        iter.index = SIZE - 1;
560        assert!(iter.next().is_some());
561
562        // When None we should no longer increase index
563        assert!(iter.next().is_none());
564        assert!(iter.index == SIZE);
565        assert!(iter.next().is_none());
566        assert!(iter.index == SIZE);
567    }
568}
bevy_reflect/list.rs

bevy_reflect/
list.rs
