110 lines
3.8 KiB
TypeScript
110 lines
3.8 KiB
TypeScript
/*
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Copyright 2020 Bruno Windels <bruno@windels.cloud>
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import {BaseObservableValue} from "./BaseObservableValue";
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import {SubscriptionHandle} from "../BaseObservable";
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export class FlatMapObservableValue<P, C> extends BaseObservableValue<C | undefined> {
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private sourceSubscription?: SubscriptionHandle;
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private targetSubscription?: SubscriptionHandle;
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constructor(
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private readonly source: BaseObservableValue<P>,
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private readonly mapper: (value: P) => (BaseObservableValue<C> | undefined)
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) {
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super();
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}
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onUnsubscribeLast() {
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super.onUnsubscribeLast();
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this.sourceSubscription = this.sourceSubscription!();
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if (this.targetSubscription) {
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this.targetSubscription = this.targetSubscription();
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}
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}
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onSubscribeFirst() {
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super.onSubscribeFirst();
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this.sourceSubscription = this.source.subscribe(() => {
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this.updateTargetSubscription();
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this.emit(this.get());
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});
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this.updateTargetSubscription();
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}
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private updateTargetSubscription() {
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const sourceValue = this.source.get();
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if (sourceValue) {
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const target = this.mapper(sourceValue);
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if (target) {
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if (!this.targetSubscription) {
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this.targetSubscription = target.subscribe(() => this.emit(this.get()));
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}
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return;
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}
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}
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// if no sourceValue or target
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if (this.targetSubscription) {
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this.targetSubscription = this.targetSubscription();
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}
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}
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get(): C | undefined {
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const sourceValue = this.source.get();
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if (!sourceValue) {
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return undefined;
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}
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const mapped = this.mapper(sourceValue);
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return mapped?.get();
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}
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}
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import {ObservableValue} from "./ObservableValue";
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export function tests() {
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return {
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"flatMap.get": assert => {
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const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
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const countProxy = new FlatMapObservableValue(a, a => a!.count);
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assert.strictEqual(countProxy.get(), undefined);
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const count = new ObservableValue<number>(0);
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a.set({count});
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assert.strictEqual(countProxy.get(), 0);
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},
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"flatMap update from source": assert => {
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const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
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const updates: (number | undefined)[] = [];
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new FlatMapObservableValue(a, a => a!.count).subscribe(count => {
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updates.push(count);
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});
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const count = new ObservableValue<number>(0);
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a.set({count});
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assert.deepEqual(updates, [0]);
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},
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"flatMap update from target": assert => {
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const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
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const updates: (number | undefined)[] = [];
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new FlatMapObservableValue(a, a => a!.count).subscribe(count => {
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updates.push(count);
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});
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const count = new ObservableValue<number>(0);
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a.set({count});
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count.set(5);
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assert.deepEqual(updates, [0, 5]);
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}
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}
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}
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