Struct Watcher 

pub struct Watcher {
    pub key: String,
    pub predicate: WatchPredicate,
    pub action: Arc<dyn Fn(Value, Value, State) -> BoxFuture<()> + Send + Sync>,
    pub blocking: bool,
}

A single state watcher: observes one key, fires an async action when the predicate matches.

Fields

key: String

The state key to observe.

predicate: WatchPredicate

The condition under which this watcher fires.

action: Arc<dyn Fn(Value, Value, State) -> BoxFuture<()> + Send + Sync>

Async action receiving (old_value, new_value, state).

blocking: bool

If true, the processor awaits this action sequentially on the control lane. If false, the processor spawns it concurrently.

Trait Implementations

impl Debug for Watcher

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

Formats the value using the given formatter.