gristlabs_grist-core/app/client/lib/koArrayWrap.ts

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import {KoArray} from 'app/client/lib/koArray';
import {IDisposableOwnerT, MutableObsArray, ObsArray, setDisposeOwner} from 'grainjs';
/**
* Returns a grainjs ObsArray that reflects the given koArray, mapping small changes using
* similarly efficient events.
*
* (Note that for both ObsArray and koArray, the main purpose in life is to be more efficient than
* an array-valued observable by handling small changes more efficiently.)
*/
export function createObsArray<T>(
owner: IDisposableOwnerT<ObsArray<T>> | null,
koArray: KoArray<T>,
): ObsArray<T> {
return setDisposeOwner(owner, new KoWrapObsArray(koArray));
}
/**
* An Observable that wraps a Knockout observable, created via fromKo(). It keeps minimal overhead
* when unused by only subscribing to the wrapped observable while it itself has subscriptions.
*
* This way, when unused, the only reference is from the wrapper to the wrapped object. KoWrapObs
* should not be disposed; its lifetime is tied to that of the wrapped object.
*/
class KoWrapObsArray<T> extends MutableObsArray<T> {
private _koSub: any = null;
constructor(_koArray: KoArray<T>) {
super(Array.from(_koArray.peek()));
this._koSub = _koArray.subscribe((splice: any) => {
const newValues = splice.array.slice(splice.start, splice.start + splice.added);
this.splice(splice.start, splice.deleted.length, ...newValues);
}, null, 'spliceChange');
}
public dispose(): void {
this._koSub.dispose();
super.dispose();
}
}