pub struct EntityGeneration(/* private fields */);
Expand description
This tracks different versions or generations of an EntityRow
.
Importantly, this can wrap, meaning each generation is not necessarily unique per EntityRow
.
This should be treated as a opaque identifier, and its internal representation may be subject to change.
§Aliasing
Internally EntityGeneration
wraps a u32
, so it can’t represent every possible generation.
Eventually, generations can (and do) wrap or alias.
This can cause Entity
and EntityGeneration
values to be equal while still referring to different conceptual entities.
This can cause some surprising behavior:
let (aliased, did_alias) = EntityGeneration::FIRST.after_versions(1u32 << 31).after_versions_and_could_alias(1u32 << 31);
assert!(did_alias);
assert!(EntityGeneration::FIRST == aliased);
This can cause some unintended side effects.
See Entity
docs for practical concerns and how to minimize any risks.
Implementations§
Source§impl EntityGeneration
impl EntityGeneration
Sourcepub const FIRST: EntityGeneration
pub const FIRST: EntityGeneration
Represents the first generation of an EntityRow
.
Sourcepub const fn to_bits(self) -> u32
pub const fn to_bits(self) -> u32
Gets some bits that represent this value. The bits are opaque and should not be regarded as meaningful.
Sourcepub const fn from_bits(bits: u32) -> EntityGeneration
pub const fn from_bits(bits: u32) -> EntityGeneration
Reconstruct an EntityGeneration
previously destructured with EntityGeneration::to_bits
.
Only useful when applied to results from to_bits
in the same instance of an application.
Sourcepub const fn after_versions(self, versions: u32) -> EntityGeneration
pub const fn after_versions(self, versions: u32) -> EntityGeneration
Returns the EntityGeneration
that would result from this many more versions
of the corresponding EntityRow
from passing.
Sourcepub const fn after_versions_and_could_alias(
self,
versions: u32,
) -> (EntityGeneration, bool)
pub const fn after_versions_and_could_alias( self, versions: u32, ) -> (EntityGeneration, bool)
Identical to after_versions
but also returns a bool
indicating if,
after these versions
, one such version could conflict with a previous one.
If this happens, this will no longer uniquely identify a version of an EntityRow
.
This is called entity aliasing.
Sourcepub const fn cmp_approx(&self, other: &EntityGeneration) -> Ordering
pub const fn cmp_approx(&self, other: &EntityGeneration) -> Ordering
Compares two generations.
Generations that are later will be Greater
than earlier ones.
let later_generation = EntityGeneration::FIRST.after_versions(400);
assert_eq!(EntityGeneration::FIRST.cmp_approx(&later_generation), Ordering::Less);
let (aliased, did_alias) = EntityGeneration::FIRST.after_versions(400).after_versions_and_could_alias(u32::MAX);
assert!(did_alias);
assert_eq!(EntityGeneration::FIRST.cmp_approx(&aliased), Ordering::Less);
Ordering will be incorrect and non-transitive for distant generations:
let later_generation = EntityGeneration::FIRST.after_versions(3u32 << 31);
let much_later_generation = later_generation.after_versions(3u32 << 31);
// while these orderings are correct and pass assertions...
assert_eq!(EntityGeneration::FIRST.cmp_approx(&later_generation), Ordering::Less);
assert_eq!(later_generation.cmp_approx(&much_later_generation), Ordering::Less);
// ... this ordering is not and the assertion fails!
assert_eq!(EntityGeneration::FIRST.cmp_approx(&much_later_generation), Ordering::Less);
Because of this, EntityGeneration
does not implement Ord
/PartialOrd
.
Trait Implementations§
Source§impl Clone for EntityGeneration
impl Clone for EntityGeneration
Source§fn clone(&self) -> EntityGeneration
fn clone(&self) -> EntityGeneration
1.0.0 · Source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moreSource§impl Debug for EntityGeneration
impl Debug for EntityGeneration
Source§impl Display for EntityGeneration
impl Display for EntityGeneration
Source§impl FromReflect for EntityGeneration
impl FromReflect for EntityGeneration
Source§fn from_reflect(
reflect: &(dyn PartialReflect + 'static),
) -> Option<EntityGeneration>
fn from_reflect( reflect: &(dyn PartialReflect + 'static), ) -> Option<EntityGeneration>
Self
from a reflected value.Source§fn take_from_reflect(
reflect: Box<dyn PartialReflect>,
) -> Result<Self, Box<dyn PartialReflect>>
fn take_from_reflect( reflect: Box<dyn PartialReflect>, ) -> Result<Self, Box<dyn PartialReflect>>
Self
using,
constructing the value using from_reflect
if that fails. Read moreSource§impl GetTypeRegistration for EntityGeneration
impl GetTypeRegistration for EntityGeneration
Source§fn get_type_registration() -> TypeRegistration
fn get_type_registration() -> TypeRegistration
TypeRegistration
for this type.Source§fn register_type_dependencies(_registry: &mut TypeRegistry)
fn register_type_dependencies(_registry: &mut TypeRegistry)
Source§impl Hash for EntityGeneration
impl Hash for EntityGeneration
Source§impl PartialEq for EntityGeneration
impl PartialEq for EntityGeneration
Source§impl PartialReflect for EntityGeneration
impl PartialReflect for EntityGeneration
Source§fn get_represented_type_info(&self) -> Option<&'static TypeInfo>
fn get_represented_type_info(&self) -> Option<&'static TypeInfo>
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fn to_dynamic(&self) -> Box<dyn PartialReflect>
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&mut self,
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fn reflect_ref(&self) -> ReflectRef<'_>
Source§fn reflect_mut(&mut self) -> ReflectMut<'_>
fn reflect_mut(&mut self) -> ReflectMut<'_>
Source§fn reflect_owned(self: Box<EntityGeneration>) -> ReflectOwned
fn reflect_owned(self: Box<EntityGeneration>) -> ReflectOwned
Source§fn try_into_reflect(
self: Box<EntityGeneration>,
) -> Result<Box<dyn Reflect>, Box<dyn PartialReflect>>
fn try_into_reflect( self: Box<EntityGeneration>, ) -> Result<Box<dyn Reflect>, Box<dyn PartialReflect>>
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Source§fn into_partial_reflect(self: Box<EntityGeneration>) -> Box<dyn PartialReflect>
fn into_partial_reflect(self: Box<EntityGeneration>) -> Box<dyn PartialReflect>
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fn is_dynamic(&self) -> bool
Source§impl Reflect for EntityGeneration
impl Reflect for EntityGeneration
Source§fn into_any(self: Box<EntityGeneration>) -> Box<dyn Any>
fn into_any(self: Box<EntityGeneration>) -> Box<dyn Any>
Box<dyn Any>
. Read moreSource§fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
&mut dyn Any
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fn into_reflect(self: Box<EntityGeneration>) -> Box<dyn Reflect>
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fn as_reflect(&self) -> &(dyn Reflect + 'static)
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fn as_reflect_mut(&mut self) -> &mut (dyn Reflect + 'static)
Source§impl TypePath for EntityGeneration
impl TypePath for EntityGeneration
Source§fn type_path() -> &'static str
fn type_path() -> &'static str
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fn short_type_path() -> &'static str
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fn type_ident() -> Option<&'static str>
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fn crate_name() -> Option<&'static str>
Source§impl Typed for EntityGeneration
impl Typed for EntityGeneration
impl Copy for EntityGeneration
impl Eq for EntityGeneration
impl StructuralPartialEq for EntityGeneration
Auto Trait Implementations§
impl Freeze for EntityGeneration
impl RefUnwindSafe for EntityGeneration
impl Send for EntityGeneration
impl Sync for EntityGeneration
impl Unpin for EntityGeneration
impl UnwindSafe for EntityGeneration
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