feat(Effects): Add lettable ofType operator

Introduces lettable operator for Actions.ofType.

BREAKING CHANGE:

Updates minimum version of RxJS dependency.

BEFORE:

Minimum peer dependency of RxJS ^5.0.0

AFTER:

Minimum peer dependency of RxJS ^5.5.0

Author: brandonroberts

modules/effects/spec/actions.spec.ts

@@ -9,7 +9,8 @@ import {
   ScannedActionsSubject,
   ActionsSubject,
 } from '@ngrx/store';
-import { Actions } from '../';
+import { Actions, ofType } from '../';
+import { map, toArray } from 'rxjs/operators';
 
 describe('Actions', function() {
   let actions$: Actions;
@@ -64,9 +65,7 @@ describe('Actions', function() {
     const expected = actions.filter(type => type === ADD);
 
     actions$
-      .ofType(ADD)
-      .map(update => update.type)
-      .toArray()
+      .pipe(ofType(ADD), map(update => update.type), toArray())
       .subscribe({
         next(actual) {
           expect(actual).toEqual(expected);

modules/effects/src/actions.ts

@@ -3,6 +3,7 @@ import { Action, ScannedActionsSubject } from '@ngrx/store';
 import { Observable } from 'rxjs/Observable';
 import { Operator } from 'rxjs/Operator';
 import { filter } from 'rxjs/operator/filter';
+import { OperatorFunction } from 'rxjs/interfaces';
 
 @Injectable()
 export class Actions<V = Action> extends Observable<V> {
@@ -22,8 +23,14 @@ export class Actions<V = Action> extends Observable<V> {
   }
 
   ofType<V2 extends V = V>(...allowedTypes: string[]): Actions<V2> {
-    return filter.call(this, (action: Action) =>
+    return ofType<any>(...allowedTypes)(this.source as Actions<V2>);
+  }
+}
+
+export function ofType<T extends Action>(...allowedTypes: string[]) {
+  return function ofTypeOperator(source$: Actions<T>): Actions<T> {
+    return filter.call(source$, (action: Action) =>
       allowedTypes.some(type => type === action.type)
     );
-  }
+  };
 }

modules/effects/src/index.ts

@@ -4,7 +4,7 @@ export {
   getEffectsMetadata,
 } from './effects_metadata';
 export { mergeEffects } from './effects_resolver';
-export { Actions } from './actions';
+export { Actions, ofType } from './actions';
 export { EffectsModule } from './effects_module';
 export { EffectSources } from './effect_sources';
 export { OnRunEffects } from './on_run_effects';