view_recipe.md

Test-Driving the Next Feature

Now that we have Angular setup, including a way to manage front-end assets, run tests, and deploy our application to production, the hard part is done. In this chapter, let's use what we've set up, along with some TDD, to implement the ability to click on a recipe in the results list and view its instructions.

In a classic Rails app, we'd have a method called show in our RecipesController, which would be routed-to from /recipes/:id. We'll do something similar in our Angular app, however we won't add this feature to the existing RecipesController.coffee, but a new controller called RecipeController.

There's no advantage to having the existing RecipesController.coffee handle the viewing of an individual recipe, other than saving us a bit of setup in the test. My feeling is that when there's no advantage over adding code to an existing class or file, it's always better to make a new class or file.

Generally, what we need to do here is:

1. Create our Angular controller
2. Create our backend Rails controller
3. Write a browser-based test for the feature
4. Create a view

Angular controller

First, we'll update our Angular app config to route /recipes/:recipeId to the yet-to-be-created RecipeController:

git://receta.git/app/assets/javascripts/app.coffee#..13ec847

Now, let's create a bare-bones version of our controller:

git://receta.git/app/assets/javascripts/controllers/RecipeController.coffee#add-recipe-controller

And the boilerplate needed for our test:

git://receta.git/spec/javascripts/controllers/RecipeController_spec.coffee#add-recipe-controller

What RecipeController needs to do is:

• Load the recipe identified by :recipeId in the URL and set it to some variable in $scope
• If the recipe doesn't exist, handle that error somehow

Lets get the happy path working first:

git://receta.git/spec/javascripts/controllers/RecipeController_spec.coffee#..62feecc

This is similar to what we had in RecipesController_spec.coffee. Because the HTTP call to our backend happens on controller startup, we create a function setupController() that handles mocking out the HTTP calls. It takes a single parameter—recipeExists—to allow us to control whether or not the backend sends a 404 or a real recipe.

Since none of this is implemented yet, our test should fail. Let's try it:

git://receta.git/#recipe-controller-test!rake teaspoon!nonzero

Sure enough, our test fails exactly how we'd like: $scope.recipe isn't defined for either case, and no HTTP calls were made, despite our expectation that they would be.

Let's make it pass. We'll use Angular's $resource service to create the same resource we did in RecipesController, but use the get method, which does what we want.

git://receta.git/app/assets/javascripts/controllers/RecipeController.coffee#..952c819

Now, we see if this makes our tests pass:

git://receta.git/#recipe-controller-test-passes!rake teaspoon

It does!

Although our code does technically handle the case of a missing recipe, it doesn't handle it very well. We'd like to pass onto the user some indication that things went wrong. In Rails, we'd use the flash as a way to provide such information.

In Angular, we can certainly create our own flash by just assigning { error: “Recipe not found”} to $scope.flash. Instead, lets use a pre-made module that will handle flash messages, but also allow us to display them in our views. angular-flash is that component, so let's install it.

First, we add it to Bowerfile:

git://receta.git/Bowerfile#..df5539b

To make sure the asset pipeline picks up this new dependency, we'll need to add it to application.js as well:

git://receta.git/app/assets/javascripts/application.js#..angular-flash-in-application-js

Note the slightly different path to the file we want–this is the lack of standardization across front-end components rearing its ugly head.

Finally, we add it as a module dependency to our app. angular-flash comes with two modules, one for the flash data itself, and another for the view components.

git://receta.git/app/assets/javascripts/app.coffee#..df5539b

We'll see how the view components work a bit later, but for now, our controller can depend on a component called flash. flash allows us to set errors, warnings, informational messages, and success messages.

Back to our test, we want to assert that the flash receives an error message that the recipe couldn't be found.

git://receta.git/spec/javascripts/controllers/RecipeController_spec.coffee#..8aa6cf7

Notice that we're taking advantage of Angular's alternate dependency injection naming convention. We want our test to use an object called flash to make assertions, but since this component isn't provided by Angular, it's name—for dependency injection purposes—is also flash, meaning we'd need to use a different name for the flash in our tests. Angular allows us to name the parameter with leading and trailing underscores, e.g. _flash_. When we do this, Angular understands that the object flash should be injected. This means that the name of the object that “escapes” the closure can be named flash. Ah, JavaScript!

Now, when we run the test, we should see a simple expectation failure on the message.

git://receta.git/#test-recipe-controller-for-flash!rake teaspoon!nonzero

With a clearly failing test, we just need to add the flash as a dependency, and use it.

git://receta.git/app/assets/javascripts/controllers/RecipeController.coffee#..b9ee91e

We add flash to the list of injected dependencies, and then set the error message in our failure callback. Sure enough, the test passes:

git://receta.git/#test-for-flash-passes!rake teaspoon

Our Angular controller is done! We still need a view, a browser-based test, and the backend. Let's do the Rails backend next.

Rails controller

In the Rails world, it is canonical to have the same controller have the code for both index and show, so what we need to do here is implement show.

First, let's add the new route to config/routes.rb:

git://receta.git/config/routes.rb#..323798b

We'll add an empty show method to the controller as well:

git://receta.git/app/controllers/recipes_controller.rb#..323798b

Finally, we'll write tests for when the recipe exists and for when it doesn't:

git://receta.git/spec/controllers/recipes_controller_spec.rb#..323798b

This should result in a failing test, which it does:

git://receta.git/#failing-recipe-show!rspec spec/controllers/recipes_controller_spec.rb!nonzero

To make this pass, we'll fetch the recipe:

git://receta.git/app/controllers/recipes_controller.rb#..5764b6e

and implement a JBuilder view that uses our existing _recipe.json.jbuilder partial:

git://receta.git/app/views/recipes/show.json.jbuilder#recipe-show-passes

To handle the case of a non-existent recipe, we'll let the ActiveRecord::RecordNotFound leak out of our controller, and use rescue_from in ApplicationController to handle that. This way, we never have to worry about translating this error into a 404 again.

git://receta.git/app/controllers/application_controller.rb#..5764b6e

Now, everything passes!

git://receta.git/#recipe-show-passes!rspec spec/controllers/recipes_controller_spec.rb

Let's bring it all together with a browser-based test.

Browser-based test

Our browser-based test will simulate a user using our app, so we'll first do a search, and then navigate to a specific recipe. We'll then check that the resulting view shows the title and instructions. We'll also navigate back to our results, assuming the existence of a “back” button.

git://receta.git/spec/features/view_spec.rb#view-spec

Running the test fails:

git://receta.git/#view-spec!rspec spec/features/view_spec.rb!nonzero

If you recall, we just used an href of # around the recipe name in the search results. Clicking that essentially clears the search and starts over.

We'll need to change that a to route us to /recipes/:recipeId, as well as actually build out the “show” view.

First, we'll change the a:

git://receta.git/app/assets/javascripts/templates/index.html#..62a1e1d

Notice that we removed the argument to href, which will keep the browser from changing its location and reloading our view. Instead, we used ng-click to trigger the view() method that we'll now add to RecipesController:

git://receta.git/app/assets/javascripts/controllers/RecipesController.coffee#..62a1e1d

All that's left is to create the view in show.html:

git://receta.git/app/assets/javascripts/templates/show.html#view-integrated

We'll also add a method to make the “Back” button work:

git://receta.git/app/assets/javascripts/controllers/RecipeController.coffee#..480fcfa

Now, everything works:

git://receta.git/#view-integrated!rspec spec/features/view_spec.rb

We added the back button and function specifically to call out a gap between what we get with Angular and what we get with Rails, with respect to view and controller implementation.

We've already seen that Angular's router requires more explicit configuration than Rails'. We can also now see that we don't get convenient methods like recipes_path or recipe_path(recipe) to generate routes for us. There doesn't seem to be a canonical way to do this at this time.

There's one last thing to do, and that's integrate the flash message.

Flash message

Although we hope to not generate links to non-existent recipes, it's still possible it could happen and, unlike a web app where a 404 will send us to a special page, since our Angular app is using AJAX requests, we'll have to do something if we get an error from the backend. We test-drove setting an error message in the flash, so now we just need to show it in our view.

The angular-flash module we installed has two parts. The first, which we've already seen, is a place to store flash messages. The second is to allow your view to “subscribe” to them, which means that you can arrange for markup to be shown if there is a flash message.

Because this is not something a user will ever be intended to see, and is also very simple, we're not going to write a test for it. If there were more complex logic around the flash, and its message, a test would be more useful, but for this case, it's not really worth it.

First, we'll add the necessary markup to show.html:

git://receta.git/app/assets/javascripts/templates/show.html#..db53af6

Our article tag has three special attributes, provided by angular-flash:

• flash-alert which binds this markup to the contents of the flash
• duration which we can use to “fade out” the flash after a time
• active-class, a class that will be added to this element when the flash has a value

The second thing we need to do is to configure angular-flash so that it knows about the various alert classes that Bootstrap provides. We do this in the app config in app.coffee:

git://receta.git/app/assets/javascripts/app.coffee#..db53af6

What this configuration means is that if there is, for example, a value in flash.error, angular-flash will add the class alert-danger to the flash element. Since we also configured that element to add alert to any flash message, our markup will be styled with the class alert alert-danger which is what Bootstrap needs to show an alert.

Now, let's navigate to a non-existent recipe and see it in action:

Perfect!

Now that we've seen how we can use TDD for all aspects of our feature, let's add the create, update, and destroy features. We'll do this very quickly as a way to demonstrate what the code looks like. You probably wouldn't add all of these at the same time in your “real” application.