Struct moxie_dom::prelude::Key[][src]

pub struct Key<State> { /* fields omitted */ }
Expand description

A Key offers access to a state variable. The key allows reads of the state variable through a snapshot taken when the Key was created. Writes are supported with Key::update and Key::set.

They are created with the cache_state and state functions.

See state and cache_state for examples.

Implementations

Returns the topo::CallId at which the state variable is bound.

Runs updater with a reference to the state variable’s latest value, and enqueues a commit to the variable if updater returns Some. Returns the Revision at which the state variable was last rooted if the variable is live, otherwise returns None.

Enqueuing the commit invokes the state change waker registered with the Runtime (if any) to ensure that the code embedding the runtime schedules another call of run_once.

This should be called during event handlers or other code which executes outside of a Revision’s execution, otherwise unpredictable waker behavior may be obtained.

Example
use futures::task::waker;
use moxie::{runtime::RunLoop, state, testing::BoolWaker};

// this runtime holds a single state variable
let mut rt = RunLoop::new(|| state(|| 0u64));

let track_wakes = BoolWaker::new();
rt.set_state_change_waker(waker(track_wakes.clone()));

let (first_commit, first_key) = rt.run_once();
assert_eq!(*first_commit, 0, "no updates yet");
assert!(!track_wakes.is_woken(), "no updates yet");

first_key.update(|_| None); // this is a no-op
assert_eq!(*first_key, 0, "no updates yet");
assert!(!track_wakes.is_woken(), "no updates yet");

first_key.update(|prev| Some(prev + 1));
assert_eq!(*first_key, 0, "update only enqueued, not yet committed");
assert!(track_wakes.is_woken());

let (second_commit, second_key) = rt.run_once(); // this commits the pending update
assert_eq!(*second_key, 1);
assert_eq!(*second_commit, 1);
assert_eq!(*first_commit, 0, "previous value still held by previous pointer");
assert!(!track_wakes.is_woken(), "wakes only come from updating state vars");
assert_eq!(first_key, second_key, "same state variable");

Commits a new state value if it is unequal to the current value and the state variable is still live. Has the same properties as update regarding waking the runtime.

See state and cache_state for examples.

Mutates a copy of the current state, committing the update if it results in a change. Has the same properties as update See state and cache_state for examples.

Trait Implementations

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

The resulting type after dereferencing.

Dereferences the value.

Formats the value using the given formatter. Read more

Feeds this value into the given Hasher. Read more

Feeds a slice of this type into the given Hasher. Read more

Keys are considered equal if they point to the same state variable. Importantly, they will compare as equal even if they contain different snapshots of the state variable due to having been initialized in different revisions.

This method tests for !=.

Auto Trait Implementations

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