rails_controllers_views_part_2.md

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Controllers & Views in Rails
Part 2

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Learning Objectives

• Write a Controller and Action To Returning Static Pages

• Specify a Default (root) Route

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Serving Static Pages

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Static Pages

• Static pages are basic HTML pages, that are not processed by a view engine like erb.

• Even dynamic web applications have a need for static pages.

• What type of static pages can you think of that might exist in a typical web application?
  Think like a user!

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Static Pages (cont.)

• So, let's say we want to display a static welcome or about page.

• So far, what has it taken to render a view in Rails?

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Static Pages (cont.)

• Does this mean that we need to create a dedicated route and action for every static page we want to view in the app?

• Heck no, that could get real yucky in a hurry, especially considering an app might have a dozen or more static pages.

• Instead, one way we can deliver any number of static pages with a single controller, and a single action, is by taking advantage of named parameters in routes!

• Let's see how...

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Static Pages - Setup

• It's that time again - time to create a new Rails app!

   ? rails new my_site -T
   ...
   ...
   ? cd my_site

• What does the -T option do?

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Static Pages - Route

• We need to determine what our route that serves static pages will be:

  • What HTTP Verb will we use?

  • What URI Path could we use? Remember, we need to be able to pass in the page we want as a paramter.

  • What Controller and Action will the route map to?

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Static Pages - Route (cont.)

• Let's go with something like this in our routes.rb:

   Rails.application.routes.draw do
  
   	get '/pages/:page', to: 'pages#show'
   
   end

• Based on this route, take a guess what value would the href  attribute in a link be set to if we wanted to view a home page?

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Static Pages - Route (cont.)

• Yes, we can put <a> tags on any page, anywhere we want that look like this:

   <a href="/pages/home">Home</a>

• As you'll see, in our show action, we can access the params hash to extract the value of "home" that was passed in.
  Perhaps you already know what code would access the value in the path after the pages segment (/pages/_______)?

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Static Pages - Controller

• As before, let's fire up our server with rails s, then browse to localhost:3000/pages/home to see the error complaining that it can't find the PagesController.

• We fixed a similar error in the previous lesson.
  What did we have to do?

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Static Pages - Controller (cont.)

• So, do this:

   ? touch app/controllers/pages_controller.rb

• Then, in pages_controller.rb write the class:

   class PagesController < ApplicationController
   
   end

• What's the next error we will see?

• How do we fix it?

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Static Pages - Code the show Action

• Now that we've stubbed up our show action in our pages controller, we've got to figure out how we're going to render the page being requested.

• First, let's find out what page has been requested.
  Again, where do we find this information?

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Static Pages - Code the show Action

• Yes, we grab it out of the params hash like this:

   def show
  		page = params[:page]
   end

• So, the params hash has a key of :page, where did this name come from?

• Great! We now have the page they want, but where are we going to put these static pages? By convention, Rails is going look in a certain folder - what is it?

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Static Pages - Code the show Action

• Let's create that folder to hold our static pages:

   ? mkdir app/views/pages

• Now, since we are requesting a home page, we better create a home.html file:

   ? touch app/views/pages/home.html

• Note that the render method will also find .html files if it does not find a .erb file.

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Static Pages - Code the show Action

• Better put something in there so that we know we got it right. Something short and to the point:

   <h1>Home</h1>

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Static Pages - Code the show Action

• If we save and refresh, we'll see an error telling us that we're Missing template pages/show.

• Why is it looking for a show view?

• We need to tell it that we want to render a view different from the default convention...

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Static Pages - Code the show Action

• As a reminder, the convention is that an action will automatically render a view that:

  • Is in a folder named: app/views/{name of the controller}.
  • With a filename matching that of the action.

• However, we can use the render method to override Rails and render a view different from this default (or render the default in a different way, e.g. skipping the layout template)...

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Static Pages - Code the show Action

• In our show action, we can use the render method like this to return the requested page:

   class PagesController < ApplicationController
   	def show
   		page = params[:page]
   		render "pages/#{page}"
   	end
   end

• Refresh - Yay!

• How could we reduce the show action code to one line?

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Static Pages - Questions

• Assuming this link on a page:
  
  <a href="/pages/contact">Contact Us</a>
  
  What do we have to do if we want our app to return the contact.html page?

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Specifying a Default Route

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Specifying a Default (Root) Route

• Users of web apps don't expect to have to enter a full URL in the address bar to access certain pages or functionality.

• Instead, they expect to be able to browse to the root, e.g. localhost:3000/, and be shown the app's landing page. From there, they can use the app's hyperlinks and/or navigation to use the app.

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Specifying a Default (Root) Route

• If we browse to our current app's root, we're going to see the familiar Rails' "Welcome aboard" page.

• Let's see how we can show our home.html page as our app's default...

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Specifying a Default (Root) Route

• We can tell a Rails app which controller#action to use as our default by writing a line of code in our routes.rb like this:

   Rails.application.routes.draw do
   
   	# The action expects a page: parameter...
   	root 'pages#show', page: 'home'
   	
   	get '/pages/:page', to: 'pages#show'
   
   end

• Note that in the majority of cases, you will be able to just specify the controller#action without parameter(s).

• Refresh!

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Final Questions

• What is a static page?

• Assuming this entry in routes.rb,
  get '/cars', to: 'cars#index',
  what code would be run if the user browsed to localhost:3000/cars?

• What route in routes.rb could we define if we wanted the URL of
  localhost:3000/
  to run the code in
  cars#index?

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References

• Rails Guide - Routing from the Outside In