Struct NextRef

pub struct NextRef<'w, 's, S: State> { /* private fields */ }

A SystemParam with read-only access to the next value of the State type S.

NOTE: The next state is only set in stone during the StateFlush schedule after ResolveStateSystems::<S>::Compute.

Example

fn spawn_new_menu(menu: NextRef<Menu>) {
    match menu.unwrap() {
        Menu::Main => spawn_main_menu(),
        Menu::Settings => spawn_settings_menu(),
    }
}

Implementations

impl<S: State> NextRef<'_, '_, S>

pub fn get(&self) -> Option<&S>

Get a read-only reference to the next state, or None if disabled.

pub fn unwrap(&self) -> &S

Get a read-only reference to the next state, or panic if disabled.

pub fn will_be_disabled(&self) -> bool

Check if the next state will be disabled.

pub fn will_be_enabled(&self) -> bool

Check if the next state will be enabled.

pub fn will_be_in<P: StatePattern<S>>(&self, pattern: &P) -> bool

Check if the next state will be enabled and match a specific StatePattern.

pub fn is_triggered(&self) -> bool

Check if S is triggered to flush in the StateFlush schedule.

Trait Implementations

impl<S: State> SystemParam for NextRef<'_, '_, S>

type State = FetchState<S>

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

type Item<'w, 's> = NextRef<'w, 's, S>

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 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 ApplyDeferred.

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

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

unsafe fn validate_param<'w, 's>( state: &'s Self::State, _system_meta: &SystemMeta, _world: UnsafeWorldCell<'w>, ) -> Result<(), SystemParamValidationError>

Validates that the param can be acquired by the get_param.

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.

impl<'w, 's, S: State> ReadOnlySystemParam for NextRef<'w, 's, S>

where Res<'w, <S as State>::Next>: ReadOnlySystemParam, StaticSystemParam<'w, 's, <<S as State>::Next as NextState>::Param>: ReadOnlySystemParam, Res<'w, TriggerStateFlush<S>>: ReadOnlySystemParam,