feat(portal): expose attached result in CdkPortalOutlet

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

Fixes #9304.

Author: crisbeto

src/cdk/portal/portal-directives.ts

@@ -52,6 +52,9 @@ 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 _result: ComponentRef<any> | EmbeddedViewRef<any> | null;
+
   constructor(
       private _componentFactoryResolver: ComponentFactoryResolver,
       private _viewContainerRef: ViewContainerRef) {
@@ -93,13 +96,19 @@ export class CdkPortalOutlet extends BasePortalOutlet implements OnInit, OnDestr
     this._attachedPortal = portal;
   }
 
+  /** Component or view reference that is attached to the portal. */
+  get result(): ComponentRef<any> | EmbeddedViewRef<any> | null {
+    return this._result;
+  }
+
   ngOnInit() {
     this._isInitialized = true;
   }
 
   ngOnDestroy() {
     super.dispose();
     this._attachedPortal = null;
+    this._result = null;
   }
 
   /**
@@ -125,6 +134,7 @@ export class CdkPortalOutlet extends BasePortalOutlet implements OnInit, OnDestr
 
     super.setDisposeFn(() => ref.destroy());
     this._attachedPortal = portal;
+    this._result = ref;
 
     return ref;
   }
@@ -140,6 +150,7 @@ export class CdkPortalOutlet extends BasePortalOutlet implements OnInit, OnDestr
     super.setDisposeFn(() => this._viewContainerRef.clear());
 
     this._attachedPortal = portal;
+    this._result = 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 +46,7 @@ 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.result instanceof ComponentRef).toBe(true);
     });
 
     it('should load a template into the portal', () => {
@@ -58,6 +60,11 @@ 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.result instanceof ComponentRef).toBe(false);
+      expect(testAppComponent.portalOutlet.result).toBeTruthy();
     });
 
     it('should project template context bindings in the portal', () => {