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node_modules/rxjs/_esm2015/operators/single.js

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+import { Subscriber } from '../Subscriber';
+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%">
+ *
+ * @throws {EmptyError} Delivers an EmptyError to the Observer's `error`
+ * callback if the Observable completes before any `next` notification was sent.
+ * @param {Function} predicate - A predicate function to evaluate items emitted by the source Observable.
+ * @return {Observable<T>} An Observable that emits the single item emitted by the source Observable that matches
+ * the predicate.
+ .
+ * @method single
+ * @owner Observable
+ */
+export function single(predicate) {
+    return (source) => source.lift(new SingleOperator(predicate, source));
+}
+class SingleOperator {
+    constructor(predicate, source) {
+        this.predicate = predicate;
+        this.source = source;
+    }
+    call(subscriber, source) {
+        return source.subscribe(new SingleSubscriber(subscriber, this.predicate, this.source));
+    }
+}
+/**
+ * We need this JSDoc comment for affecting ESDoc.
+ * @ignore
+ * @extends {Ignored}
+ */
+class SingleSubscriber extends Subscriber {
+    constructor(destination, predicate, source) {
+        super(destination);
+        this.predicate = predicate;
+        this.source = source;
+        this.seenValue = false;
+        this.index = 0;
+    }
+    applySingleValue(value) {
+        if (this.seenValue) {
+            this.destination.error('Sequence contains more than one element');
+        }
+        else {
+            this.seenValue = true;
+            this.singleValue = value;
+        }
+    }
+    _next(value) {
+        const index = this.index++;
+        if (this.predicate) {
+            this.tryNext(value, index);
+        }
+        else {
+            this.applySingleValue(value);
+        }
+    }
+    tryNext(value, index) {
+        try {
+            if (this.predicate(value, index, this.source)) {
+                this.applySingleValue(value);
+            }
+        }
+        catch (err) {
+            this.destination.error(err);
+        }
+    }
+    _complete() {
+        const destination = this.destination;
+        if (this.index > 0) {
+            destination.next(this.seenValue ? this.singleValue : undefined);
+            destination.complete();
+        }
+        else {
+            destination.error(new EmptyError);
+        }
+    }
+}
+//# sourceMappingURL=single.js.map