63 lines
2.0 KiB
TypeScript
63 lines
2.0 KiB
TypeScript
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// (C) Copyright 2015 Moodle Pty Ltd.
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//
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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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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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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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import { FormControl } from '@angular/forms';
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import { Observable, OperatorFunction } from 'rxjs';
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import { filter } from 'rxjs/operators';
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/**
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* Create an observable that emits the current form control value.
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*
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* @param control Form control.
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* @returns Form control value observable.
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*/
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export function formControlValue<T = unknown>(control: FormControl): Observable<T> {
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return control.valueChanges.pipe(
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startWithOnSubscribed(() => control.value),
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filter(value => value !== null),
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);
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}
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/**
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* Observable operator that waits for a promise to resolve before emitting the result.
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*
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* @returns Operator.
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*/
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export function resolved<T>(): OperatorFunction<Promise<T>, T> {
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return source => new Observable(subscriber => {
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const subscription = source.subscribe(async promise => {
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const value = await promise;
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return subscriber.next(value);
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});
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return subscription;
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});
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}
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/**
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* Same as the built-in startWith operator, but evaluates the starting value for each subscriber
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* on subscription.
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*
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* @param onSubscribed Callback to calculate the starting value.
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* @returns Operator.
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*/
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export function startWithOnSubscribed<T>(onSubscribed: () => T): OperatorFunction<T, T> {
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return source => new Observable(subscriber => {
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subscriber.next(onSubscribed());
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return source.subscribe(value => subscriber.next(value));
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});
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}
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