Code coverage report for src/operator/single.ts

Statements: 100% (44 / 44)      Branches: 100% (12 / 12)      Functions: 100% (9 / 9)      Lines: 100% (41 / 41)      Ignored: none     

All files » src/operator/ » single.ts
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import {Observable} from '../Observable';
import {Operator} from '../Operator';
import {Subscriber} from '../Subscriber';
import {Observer} from '../Observer';
 
import {tryCatch} from '../util/tryCatch';
import {errorObject} from '../util/errorObject';
import {EmptyError} from '../util/EmptyError';
 
/**
 * Returns an Observable that emits the single item emitted by the source Observable that matches a specified
 * predicate, if that Observable emits one such item. If the source Observable emits more than one such item or no
 * such items, notify of an IllegalArgumentException or NoSuchElementException respectively.
 *
 * <img src="./img/single.png" width="100%">
 *
 * @param {Function} a predicate function to evaluate items emitted by the source Observable.
 * @returns {Observable<T>} an Observable that emits the single item emitted by the source Observable that matches
 * the predicate.
 .
 */
export function single<T>(predicate?: (value: T, index: number, source: Observable<T>) => boolean): Observable<T> {
  return this.lift(new SingleOperator(predicate, this));
}
 
class SingleOperator<T> implements Operator<T, T> {
  constructor(private predicate?: (value: T, index: number, source: Observable<T>) => boolean,
              private source?: Observable<T>) {
  }
 
  call(subscriber: Subscriber<T>): Subscriber<T> {
    return new SingleSubscriber(subscriber, this.predicate, this.source);
  }
}
 
class SingleSubscriber<T> extends Subscriber<T> {
  private seenValue: boolean = false;
  private singleValue: T;
  private index: number = 0;
 
  constructor(destination: Observer<T>,
              private predicate?: (value: T, index: number, source: Observable<T>) => boolean,
              private source?: Observable<T>) {
    super(destination);
  }
 
  private applySingleValue(value: T): void {
    if (this.seenValue) {
      this.destination.error('Sequence contains more than one element');
    } else {
      this.seenValue = true;
      this.singleValue = value;
    }
  }
 
  protected _next(value: T): void {
    const predicate = this.predicate;
    const currentIndex = this.index++;
 
    if (predicate) {
      let result = tryCatch(predicate)(value, currentIndex, this.source);
      if (result === errorObject) {
        this.destination.error(errorObject.e);
      } else if (result) {
        this.applySingleValue(value);
      }
    } else {
      this.applySingleValue(value);
    }
  }
 
  protected _complete(): void {
    const destination = this.destination;
 
    if (this.index > 0) {
      destination.next(this.seenValue ? this.singleValue : undefined);
      destination.complete();
    } else {
      destination.error(new EmptyError);
    }
  }
}