feat(find): add higher-order lettable version of find

ReactiveX · Aug 9, 2017 · ff6d5af · ff6d5af
1 parent cfeae9f
commit ff6d5af
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Showing 4 changed files with 110 additions and 60 deletions.
diff --git a/src/operator/find.ts b/src/operator/find.ts
@@ -1,6 +1,5 @@
 import { Observable } from '../Observable';
-import { Operator } from '../Operator';
-import { Subscriber } from '../Subscriber';
+import { find as higherOrder } from '../operators';
 
 /* tslint:disable:max-line-length */
 export function find<T, S extends T>(this: Observable<T>,
@@ -46,61 +45,5 @@ export function find<T>(this: Observable<T>,
  */
 export function find<T>(this: Observable<T>, predicate: (value: T, index: number, source: Observable<T>) => boolean,
                         thisArg?: any): Observable<T> {
-  if (typeof predicate !== 'function') {
-    throw new TypeError('predicate is not a function');
-  }
-  return <any>this.lift<any>(new FindValueOperator(predicate, this, false, thisArg));
-}
-
-export class FindValueOperator<T> implements Operator<T, T> {
-  constructor(private predicate: (value: T, index: number, source: Observable<T>) => boolean,
-              private source: Observable<T>,
-              private yieldIndex: boolean,
-              private thisArg?: any) {
-  }
-
-  call(observer: Subscriber<T>, source: any): any {
-    return source.subscribe(new FindValueSubscriber(observer, this.predicate, this.source, this.yieldIndex, this.thisArg));
-  }
-}
-
-/**
- * We need this JSDoc comment for affecting ESDoc.
- * @ignore
- * @extends {Ignored}
- */
-export class FindValueSubscriber<T> extends Subscriber<T> {
-  private index: number = 0;
-
-  constructor(destination: Subscriber<T>,
-              private predicate: (value: T, index: number, source: Observable<T>) => boolean,
-              private source: Observable<T>,
-              private yieldIndex: boolean,
-              private thisArg?: any) {
-    super(destination);
-  }
-
-  private notifyComplete(value: any): void {
-    const destination = this.destination;
-
-    destination.next(value);
-    destination.complete();
-  }
-
-  protected _next(value: T): void {
-    const { predicate, thisArg } = this;
-    const index = this.index++;
-    try {
-      const result = predicate.call(thisArg || this, value, index, this.source);
-      if (result) {
-        this.notifyComplete(this.yieldIndex ? index : value);
-      }
-    } catch (err) {
-      this.destination.error(err);
-    }
-  }
-
-  protected _complete(): void {
-    this.notifyComplete(this.yieldIndex ? -1 : undefined);
-  }
+  return higherOrder(predicate, thisArg)(this);
 }
diff --git a/src/operator/findIndex.ts b/src/operator/findIndex.ts
@@ -1,5 +1,5 @@
 import { Observable } from '../Observable';
-import { FindValueOperator } from './find';
+import { FindValueOperator } from '../operators/find';
 
 /**
  * Emits only the index of the first value emitted by the source Observable that

diff --git a/src/operators/find.ts b/src/operators/find.ts
@@ -0,0 +1,106 @@
+import { Observable } from '../Observable';
+import { Operator } from '../Operator';
+import { Subscriber } from '../Subscriber';
+import { OperatorFunction, MonoTypeOperatorFunction } from '../interfaces';
+
+export function find<T, S extends T>(predicate: (value: T, index: number, source: Observable<T>) => value is S,
+                                     thisArg?: any): OperatorFunction<T, S>;
+export function find<T, S extends T>(predicate: (value: T, index: number) => value is S,
+                                     thisArg?: any): OperatorFunction<T, S>;
+export function find<T>(predicate: (value: T, index: number, source: Observable<T>) => boolean,
+                        thisArg?: any): MonoTypeOperatorFunction<T>;
+export function find<T>(predicate: (value: T, index: number) => boolean,
+                        thisArg?: any): MonoTypeOperatorFunction<T>;
+/**
+ * Emits only the first value emitted by the source Observable that meets some
+ * condition.
+ *
+ * <span class="informal">Finds the first value that passes some test and emits
+ * that.</span>
+ *
+ * <img src="./img/find.png" width="100%">
+ *
+ * `find` searches for the first item in the source Observable that matches the
+ * specified condition embodied by the `predicate`, and returns the first
+ * occurrence in the source. Unlike {@link first}, the `predicate` is required
+ * in `find`, and does not emit an error if a valid value is not found.
+ *
+ * @example <caption>Find and emit the first click that happens on a DIV element</caption>
+ * var clicks = Rx.Observable.fromEvent(document, 'click');
+ * var result = clicks.find(ev => ev.target.tagName === 'DIV');
+ * result.subscribe(x => console.log(x));
+ *
+ * @see {@link filter}
+ * @see {@link first}
+ * @see {@link findIndex}
+ * @see {@link take}
+ *
+ * @param {function(value: T, index: number, source: Observable<T>): boolean} predicate
+ * A function called with each item to test for condition matching.
+ * @param {any} [thisArg] An optional argument to determine the value of `this`
+ * in the `predicate` function.
+ * @return {Observable<T>} An Observable of the first item that matches the
+ * condition.
+ * @method find
+ * @owner Observable
+ */
+export function find<T>(predicate: (value: T, index: number, source: Observable<T>) => boolean,
+                        thisArg?: any): MonoTypeOperatorFunction<T> {
+  if (typeof predicate !== 'function') {
+    throw new TypeError('predicate is not a function');
+  }
+  return (source: Observable<T>) => source.lift(new FindValueOperator(predicate, source, false, thisArg));
+}
+
+export class FindValueOperator<T> implements Operator<T, T> {
+  constructor(private predicate: (value: T, index: number, source: Observable<T>) => boolean,
+              private source: Observable<T>,
+              private yieldIndex: boolean,
+              private thisArg?: any) {
+  }
+
+  call(observer: Subscriber<T>, source: any): any {
+    return source.subscribe(new FindValueSubscriber(observer, this.predicate, this.source, this.yieldIndex, this.thisArg));
+  }
+}
+
+/**
+ * We need this JSDoc comment for affecting ESDoc.
+ * @ignore
+ * @extends {Ignored}
+ */
+export class FindValueSubscriber<T> extends Subscriber<T> {
+  private index: number = 0;
+
+  constructor(destination: Subscriber<T>,
+              private predicate: (value: T, index: number, source: Observable<T>) => boolean,
+              private source: Observable<T>,
+              private yieldIndex: boolean,
+              private thisArg?: any) {
+    super(destination);
+  }
+
+  private notifyComplete(value: any): void {
+    const destination = this.destination;
+
+    destination.next(value);
+    destination.complete();
+  }
+
+  protected _next(value: T): void {
+    const { predicate, thisArg } = this;
+    const index = this.index++;
+    try {
+      const result = predicate.call(thisArg || this, value, index, this.source);
+      if (result) {
+        this.notifyComplete(this.yieldIndex ? index : value);
+      }
+    } catch (err) {
+      this.destination.error(err);
+    }
+  }
+
+  protected _complete(): void {
+    this.notifyComplete(this.yieldIndex ? -1 : undefined);
+  }
+}
diff --git a/src/operators/index.ts b/src/operators/index.ts
@@ -26,6 +26,7 @@ export { exhaustMap } from './exhaustMap';
 export { expand } from './expand';
 export { filter } from './filter';
 export { finalize } from './finalize';
+export { find } from './find';
 export { ignoreElements } from './ignoreElements';
 export { map } from './map';
 export { materialize } from './materialize';