feat(dialog): add beforeClose method

Author: willshowell

src/lib/dialog/dialog-ref.ts

@@ -15,7 +15,7 @@ import {RxChain, first, filter} from '../core/rxjs/index';
 
 
 // TODO(jelbourn): resizing
-// TODO(jelbourn): afterOpen and beforeClose
+// TODO(jelbourn): afterOpen
 
 // Counter for unique dialog ids.
 let uniqueId = 0;
@@ -33,6 +33,9 @@ export class MdDialogRef<T> {
   /** Subject for notifying the user that the dialog has finished closing. */
   private _afterClosed: Subject<any> = new Subject();
 
+  /** Subject for notifying the user that the dialog has started closing. */
+  private _beforeClose: Subject<any> = new Subject();
+
   /** Result to be passed to afterClosed. */
   private _result: any;
 
@@ -63,7 +66,11 @@ export class MdDialogRef<T> {
     RxChain.from(this._containerInstance._animationStateChanged)
       .call(filter, event => event.phaseName === 'start')
       .call(first)
-      .subscribe(() => this._overlayRef.detachBackdrop());
+      .subscribe(() => {
+        this._beforeClose.next(dialogResult);
+        this._beforeClose.complete();
+        this._overlayRef.detachBackdrop();
+      });
 
     this._containerInstance._startExitAnimation();
   }
@@ -75,6 +82,13 @@ export class MdDialogRef<T> {
     return this._afterClosed.asObservable();
   }
 
+  /**
+   * Gets an observable that is notified when the dialog has started closing.
+   */
+  beforeClose(): Observable<any> {
+    return this._beforeClose.asObservable();
+  }
+
   /**
    * Updates the dialog's position.
    * @param position New dialog position.

src/lib/dialog/dialog.spec.ts

@@ -141,6 +141,20 @@ describe('MdDialog', () => {
     });
   }));
 
+  it('should close a dialog and get back a result before it is closed', async(() => {
+    let dialogRef = dialog.open(PizzaMsg, { viewContainerRef: testViewContainerRef });
+    let beforeCloseCallback = jasmine.createSpy('beforeClose callback');
+
+    dialogRef.beforeClose().subscribe(beforeCloseCallback);
+    dialogRef.close('Bulbasaurus');
+    viewContainerFixture.detectChanges();
+
+    viewContainerFixture.whenStable().then(() => {
+      expect(beforeCloseCallback).toHaveBeenCalledWith('Bulbasaurus');
+      expect(overlayContainerElement.querySelector('md-dialog-container')).toBeNull();
+    });
+  }));
+
   it('should close a dialog via the escape key', async(() => {
     dialog.open(PizzaMsg, {
       viewContainerRef: testViewContainerRef