Implement BaseView#preDestroy hook

Use a test-driven development approach to define acceptance criteria for
the method *before* writing the implementation. This aspect of our
process is not especially useful for other developers, so the individual
commits have been "squashed" together.

src/modules/components/photo/webcam.js

@@ -13,18 +13,14 @@ define(function(require) {
       this.collection = options.collection;
     },
 
-    // Override the default implementation of `destroy` to avoid a known bug in
-    // Google Chrome that keeps the camera running even after destroying the
-    // video element. Call the original implementation to preserve expected
-    // behavior.
-    destroy: function() {
+    // Avoid a known bug in Google Chrome that keeps the camera running even
+    // after destroying the video element.
+    preDestroy: function() {
       var video = this.$('video')[0];
 
       if (video) {
         video.src = undefined;
       }
-
-      return BaseView.prototype.destroy.apply(this, arguments);
     },
 
     filterAndSave: function() {

src/modules/core/base-view.js

@@ -7,7 +7,13 @@ define(function(require) {
 
   var BaseView = Backbone.View.extend({
 
+    preDestroy: function() {},
+
     destroy: function() {
+      // In case an instance has specialized logic for cleaning itself up,
+      // invoke the `preDestroy` hook before any actual destruction occurs.
+      this.preDestroy();
+
       this.stopListening();
       this.$el.empty();
 

src/modules/layouts/one-row.js

@@ -22,14 +22,10 @@ define(function(require) {
       return this;
     },
 
-    // Override the default implementation of `destroy` to remove the element's
-    // class. Call the original implementation to preserve expected behavior.
-    destroy: function() {
-      // remove the container class name before we empty
-      // the element.
+    // remove the container class name before we empty
+    // the element.
+    preDestroy: function() {
       this.$el.removeClass('single');
-
-      return BaseLayout.prototype.destroy.call(this, arguments);
     }
   });
 

test/unit/tests/base-layout.js

@@ -91,6 +91,21 @@ define(function(require) {
 
         sinon.assert.callCount(this.subView.destroy, 1);
       });
+
+      test(
+        'Invokes the `preDestroy` method prior to removing the layout element',
+        function() {
+          var layout = this.layout;
+          layout.render();
+          sinon.stub(layout, 'preDestroy', function() {
+            assert.equal(layout.$('.b').length, 1);
+          });
+
+          layout.destroy();
+
+          sinon.assert.callCount(layout.preDestroy, 1);
+        }
+      );
     });
   });
 });

test/unit/tests/base-view.js

@@ -59,6 +59,24 @@ define(['modules/core/base-view'], function(BaseView) {
 
         assert.equal(this.view.$el.contents().length, 0);
       });
+
+      test(
+        'invokes custom `preDestroy` hook prior to emptying the view',
+        function() {
+          var view = this.view;
+          view.template = sinon.stub().returns('<p>');
+
+          sinon.stub(this.view, 'preDestroy', function() {
+            assert.equal(view.$('p').length, 1);
+          });
+
+          view.render();
+          this.view.destroy();
+
+          sinon.assert.callCount(this.view.preDestroy, 1);
+          assert.equal(view.$('p').length, 0);
+        }
+      );
     });
   });
 });