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Action
You can call an Action a simplified form of a Unit as they share the same base API, although configured in a slightly different way.
- It extends the RxJS Observable class, hence it's an Observable.
- By default, It doesn't replay when subscribed to, unlike a Unit.
- It doesn't require an initial value, yet provides direct access to the last emitted value, just like a Unit.
- It can only cache one value at a time, unlike a Unit.
- Unlike Units, it doesn't perform any checks on
dispatch
.
// create an Action, that accepts number as its value
const multiplyAction = new Action<number>();
Action is an Observable but not a Subject.
multiplyAction instanceof Subject // false
multiplyAction instanceof Observable // true
// access the value
console.log(multiplyAction.value()) // logs undefined
// dynamically access the value
multiplyAction.subscribe(value => {
console.log(value) // will log future values
// do something with the value here
});
// dispatch a value
multiplyAction.dispatch(3);
// replay the value
multiplyAction.replay(); // multiplyAction emits 3 again
The above example shows the basic usage of an Action, it's similar to an RxJS Subject with slight differences.
The real-life usage would most probably be to create streams using the Action.
// create a NumUnit to apply the multiplyAction on it
const numUnit = new NumUnit({initialValue: 10})
// create a stream using the earlier Action and above Unit
const subscription = multiplyAction.pipe(
tap(multiplier => {
// multiply the numUnit's value and update it
numUnit.dispatch(currValue => currValue * multiplier)
})
).subscribe();
// or simply use the built-in createStream method
const stream = multiplyAction.createStream(action$ => {
return action$.pipe(
tap(multiplier => {
// multiply the numUnit's value and update it
numUnit.dispatch(currValue => currValue * multiplier)
})
)
})
The advantage of using the
createStream
method is that we get a Stream instance.
So we can stop and re-start the multiplication stream.// stop the multiplication stream
stream.unsubscribe();
// re-start the multiplication stream
stream.resubscribe();
| Action | Unit | BehaviorSubject |
Replays value on subscription (by default) | ❌ | ✅ | ✅ |
Can be configured to replay value on subscription | ✅ | ✅ | ❌ |
Allows to listen to only future values (useful when configured to replay on subscription) | ✅ | ✅ | ❌ |
Accepts an initial-value | ✅ | ✅ | ✅ |
Can cache more than one value | ❌ | ✅ | ❌ |
Validates dispatched values | ❌ | ✅ | ❌ |
Can re-emit/replay last value manually | ✅ | ✅ | ❌ |
✅ | ✅ | ❌ |
The configuration options can be passed at the time of instantiation. All the configuration options are optional. Some options can also be set globally. See Configuration for more details.
Last modified 2yr ago