Struct SubscriberState 

pub struct SubscriberState { /* private fields */ }

Stores the possible states a subscriber can be in. Useful to track the state of an unknown upstream source of signals based only on those signals.

Debug asserts ensure that no invalid state changes happen, like changing a completed state into an errored one, or trying to call unsubscribe twice.

By default it’s in the “waiting” state.

Implementations

impl SubscriberState

pub fn is_waiting(&self) -> bool

Is considered “waiting” when nothing had happened yet.

This flag starts as true and cannot be set. Once false, stays false.

pub fn is_primed(&self) -> bool

Is considered “primed” when it had seen at least one next call.

This flag cannot be unset, once true, stays true.

pub fn is_completed(&self) -> bool

Is considered “completed” once it is marked as completed. After which, only unsubscribe can be called, everything else will panic in debug builds.

This flag cannot be unset, once true, stays true.

pub fn is_completed_but_not_primed(&self) -> bool

True when the state was completed without ever seeing a single next!

pub fn is_errored(&self) -> bool

Is “errored” once it is marked as errored. After which, only unsubscribe can be called, everything else will panic in debug builds.

This flag cannot be unset, once true, stays true.

pub fn is_unsubscribed(&self) -> bool

Is “unsubscribed” once it is marked as unsubscribed. After which, only unsubscribe can be called, everything else will panic in debug builds.

This flag cannot be unset, once true, stays true.

pub fn is_closed(&self) -> bool

It’s considered “closed” once it’s either unsubscribed, or finished, meaning it either completed or errored.

This flag cannot be unset, once true, stays true.

pub fn is_finished(&self) -> bool

It’s considered “finished” once it’s either completed or errored.

This flag cannot be unset, once true, stays true.

pub fn is_closed_but_primed(&self) -> bool

True when closed, but also primed! Useful to see if something has useful value, and will definitely not get a new one.

pub fn is_closed_but_not_primed(&self) -> bool

True if it’s closed but hadn’t received a next call. Useful to see if something never had a useful value, and will definitely not have one.

pub fn is_closed_but_not_primed_and_not_completed(&self) -> bool

pub fn is_closed_but_not_completed(&self) -> bool

pub fn is_closed_but_not_errored(&self) -> bool

pub fn is_closed_but_not_completed_and_primed(&self) -> bool

pub fn next(&mut self)

Marks it as no longer waiting, and primed.

It will panic in debug builds when called from an already closed state.

pub fn complete(&mut self)

Marks it as completed and no longer waiting.

It will panic in debug builds when called from an already closed state.

pub fn error(&mut self)

Marks it as errored and no longer waiting.

It will panic in debug builds when called from an already closed state.

pub fn unsubscribe(&mut self)

Marks it as unsubscribed and no longer waiting.

It will panic in debug builds when called from an already unsubscribed state.

pub fn unsubscribe_if_not_already(&mut self)

Marks it as unsubscribed and no longer waiting.

Does the same thing as unsubscribe but it will never panic even if it was already marked as unsubscribed.

Unlike with complete/error, which should definitely never happen twice, sometimes the steps to unsubscribe has to be performed differently, when erroring/completing, which may or may not happen before doing an unsubscribe.

Therefore this method is more like a “make sure it’s closed” kind of method, but one should always prefer using unsubscribe here on SubscriberState, to catch double unsubscribes.

pub fn update_with_notification<In, InError>( &mut self, notification: &SubscriberNotification<In, InError>, )

where In: Signal, InError: Signal,

Applies this notification to the state.

It will panic in debug builds when an invalid state change is attempted.

pub fn notification_matches_state<In, InError>( &mut self, notification: &SubscriberNotification<In, InError>, ) -> bool

where In: Signal, InError: Signal,

Try to avoid using this function! It’s an escape hatch, and a tool to help narrow down problems.

If using this check before updating the state is what makes your logic work, it means you’re double updating with the same notification. Or upstream is incorrect by sending the same signal multiple times, in which case the problem is not you.

Rest assured these invalid update panics only happen in debug builds!

pub fn update_with_notification_would_be_invalid<In, InError>( &self, notification: &SubscriberNotification<In, InError>, ) -> bool

where In: Signal, InError: Signal,

Try to avoid using this function! It’s an escape hatch, and a tool to help narrow down problems.

If you haven’t yet, try using notification_matches_state as your safety check before reaching for this function, that one can reveal a narrower problem.

If using this check before updating the state is what makes your logic work, it means you’re either double updating with the same notification, or you apply a notification that is not a correct state change.

True for all sources of signals: Zero or more Next notifications come first, after which up to 1 Error or Complete signal, and then finally an Unsubscribe signal, and then nothing else.

Or upstream is incorrect by sending the same signal multiple times, in which case the problem is not you.

Rest assured these invalid update panics only happen in debug builds!

Trait Implementations

impl Clone for SubscriberState

fn clone(&self) -> SubscriberState

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for SubscriberState

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

Formats the value using the given formatter.

impl Default for SubscriberState

fn default() -> SubscriberState

Returns the “default value” for a type.

impl Ord for SubscriberState

fn cmp(&self, other: &SubscriberState) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for SubscriberState

fn eq(&self, other: &SubscriberState) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for SubscriberState

fn partial_cmp(&self, other: &SubscriberState) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for SubscriberState

impl Eq for SubscriberState

impl StructuralPartialEq for SubscriberState