Struct SystemChangeTick

pub struct SystemChangeTick { /* private fields */ }

A SystemParam that reads the previous and current change ticks of the system.

A system’s change ticks are updated each time it runs:

• last_run copies the previous value of change_tick
• this_run copies the current value of World::read_change_tick

Component change ticks that are more recent than last_run will be detected by the system. Those can be read by calling last_changed on a Mut<T> or ResMut<T>.

Implementations

impl SystemChangeTick

pub fn this_run(&self) -> Tick

Returns the current World change tick seen by the system.

pub fn last_run(&self) -> Tick

Returns the World change tick seen by the system the previous time it ran.

Trait Implementations

impl Debug for SystemChangeTick

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl SystemParam for SystemChangeTick

type State = ()

Used to store data which persists across invocations of a system.

type Item<'w, 's> = SystemChangeTick

The item type returned when constructing this system param. The value of this associated type should be Self, instantiated with new lifetimes.

fn init_state(_world: &mut World, _system_meta: &mut SystemMeta) -> Self::State

Registers any World access used by this SystemParam and creates a new instance of this param’s State.

unsafe fn get_param<'w, 's>( _state: &'s mut Self::State, system_meta: &SystemMeta, _world: UnsafeWorldCell<'w>, change_tick: Tick, ) -> Self::Item<'w, 's>

Creates a parameter to be passed into a SystemParamFunction.

unsafe fn new_archetype( state: &mut Self::State, archetype: &Archetype, system_meta: &mut SystemMeta, )

For the specified Archetype, registers the components accessed by this SystemParam (if applicable).a

fn apply(state: &mut Self::State, system_meta: &SystemMeta, world: &mut World)

Applies any deferred mutations stored in this SystemParam’s state. This is used to apply Commands during apply_deferred.

fn queue( state: &mut Self::State, system_meta: &SystemMeta, world: DeferredWorld<'_>, )

Queues any deferred mutations to be applied at the next apply_deferred.

unsafe fn validate_param( _state: &Self::State, _system_meta: &SystemMeta, _world: UnsafeWorldCell<'_>, ) -> bool

Validates that the param can be acquired by the get_param. Built-in executors use this to prevent systems with invalid params from running. For nested SystemParams validation will fail if any delegated validation fails.

impl ReadOnlySystemParam for SystemChangeTick