feat(portal): expose attached result in CdkPortalOutlet (#9326)

Exposes the attach `ComponentRef` or `EmbeddedViewRef` in the `CdkPortalOutlet` directive.

Fixes #9304.

src/cdk/portal/portal-directives.ts

@@ -17,6 +17,8 @@ import {
   OnDestroy,
   OnInit,
   Input,
+  EventEmitter,
+  Output,
 } from '@angular/core';
 import {Portal, TemplatePortal, ComponentPortal, BasePortalOutlet} from './portal';
 
@@ -35,6 +37,11 @@ export class CdkPortal extends TemplatePortal<any> {
   }
 }
 
+/**
+ * Possible attached references to the CdkPortalOutlet.
+ */
+export type CdkPortalOutletAttachedRef = ComponentRef<any> | EmbeddedViewRef<any> | null;
+
 
 /**
  * Directive version of a PortalOutlet. Because the directive *is* a PortalOutlet, portals can be
@@ -52,6 +59,9 @@ export class CdkPortalOutlet extends BasePortalOutlet implements OnInit, OnDestr
   /** Whether the portal component is initialized. */
   private _isInitialized = false;
 
+  /** Reference to the currently-attached component/view ref. */
+  private _attachedRef: CdkPortalOutletAttachedRef;
+
   constructor(
       private _componentFactoryResolver: ComponentFactoryResolver,
       private _viewContainerRef: ViewContainerRef) {
@@ -93,6 +103,14 @@ export class CdkPortalOutlet extends BasePortalOutlet implements OnInit, OnDestr
     this._attachedPortal = portal;
   }
 
+  @Output('attached') attached: EventEmitter<CdkPortalOutletAttachedRef> =
+      new EventEmitter<CdkPortalOutletAttachedRef>();
+
+  /** Component or view reference that is attached to the portal. */
+  get attachedRef(): CdkPortalOutletAttachedRef {
+    return this._attachedRef;
+  }
+
   ngOnInit() {
     this._isInitialized = true;
   }
@@ -100,6 +118,7 @@ export class CdkPortalOutlet extends BasePortalOutlet implements OnInit, OnDestr
   ngOnDestroy() {
     super.dispose();
     this._attachedPortal = null;
+    this._attachedRef = null;
   }
 
   /**
@@ -125,6 +144,8 @@ export class CdkPortalOutlet extends BasePortalOutlet implements OnInit, OnDestr
 
     super.setDisposeFn(() => ref.destroy());
     this._attachedPortal = portal;
+    this._attachedRef = ref;
+    this.attached.emit(ref);
 
     return ref;
   }
@@ -140,6 +161,8 @@ export class CdkPortalOutlet extends BasePortalOutlet implements OnInit, OnDestr
     super.setDisposeFn(() => this._viewContainerRef.clear());
 
     this._attachedPortal = portal;
+    this._attachedRef = viewRef;
+    this.attached.emit(viewRef);
 
     return viewRef;
   }

src/cdk/portal/portal.spec.ts

@@ -10,7 +10,8 @@ import {
   Optional,
   Injector,
   ApplicationRef,
-  TemplateRef
+  TemplateRef,
+  ComponentRef,
 } from '@angular/core';
 import {CommonModule} from '@angular/common';
 import {CdkPortal, CdkPortalOutlet, PortalModule} from './portal-directives';
@@ -45,6 +46,9 @@ describe('Portals', () => {
       // Expect that the content of the attached portal is present.
       expect(hostContainer.textContent).toContain('Pizza');
       expect(testAppComponent.portalOutlet.portal).toBe(componentPortal);
+      expect(testAppComponent.portalOutlet.attachedRef instanceof ComponentRef).toBe(true);
+      expect(testAppComponent.attachedSpy)
+          .toHaveBeenCalledWith(testAppComponent.portalOutlet.attachedRef);
     });
 
     it('should load a template into the portal', () => {
@@ -58,6 +62,13 @@ describe('Portals', () => {
       // Expect that the content of the attached portal is present and no context is projected
       expect(hostContainer.textContent).toContain('Banana');
       expect(testAppComponent.portalOutlet.portal).toBe(templatePortal);
+
+      // We can't test whether it's an instance of an `EmbeddedViewRef` so
+      // we verify that it's defined and that it's not a ComponentRef.
+      expect(testAppComponent.portalOutlet.attachedRef instanceof ComponentRef).toBe(false);
+      expect(testAppComponent.portalOutlet.attachedRef).toBeTruthy();
+      expect(testAppComponent.attachedSpy)
+          .toHaveBeenCalledWith(testAppComponent.portalOutlet.attachedRef);
     });
 
     it('should project template context bindings in the portal', () => {
@@ -499,7 +510,7 @@ class ArbitraryViewContainerRefComponent {
   selector: 'portal-test',
   template: `
   <div class="portal-container">
-    <ng-template [cdkPortalOutlet]="selectedPortal"></ng-template>
+    <ng-template [cdkPortalOutlet]="selectedPortal" (attached)="attachedSpy($event)"></ng-template>
   </div>
 
   <ng-template cdk-portal>Cake</ng-template>
@@ -524,6 +535,7 @@ class PortalTestApp {
   selectedPortal: Portal<any>|undefined;
   fruit: string = 'Banana';
   fruits = ['Apple', 'Pineapple', 'Durian'];
+  attachedSpy = jasmine.createSpy('attached spy');
 
   constructor(public injector: Injector) { }