Creating Routes in Discourse and Showing Data

Discourse
Thu, 18 Aug 2016 20:18:49 +0000
Developer Guides

Over time Discourse has grown in complexity and it can be daunting for beginners to understand how data gets all the way from the back end Ruby on Rails application to the Ember.js application in front.

This tutorial is meant to show the full lifecycle of a request in Discourse and explain the steps necessary if you want to build a new page with its own URL in our application.

URLs First

I always prefer to start thinking of features in terms of the URLs to access them. For example let’s say we want to build an admin feature that showed the last snack I ate while working on Discourse. A suitable URL for that would be /admin/snack

In this case:

Visiting /admin/snack in your browser should show the snack using the “full stack”, in other words the Ember application will be loaded up and it would request the data it needs to display the snack.

Visiting /admin/snack.json should return the JSON data for the snack itself.

The Server Side (Ruby on Rails)

Let’s start by creating a new controller for the snack.

app/controllers/admin/snack_controller.rb

class Admin::SnackController < Admin::AdminController
  def index
    render json: { name: "donut", description: "delicious!" }
  end
end

In this case we inherit from Admin::AdminController to gain all the security checks to make sure the user viewing the controller is an administrator. We just have one more thing to do to before we can access our controller, and that’s to add a line to config/routes.rb:

Find the block that looks like this:

namespace :admin, constraints: StaffConstraint.new do
  # lots of stuff
end

And add this line inside it:

get 'snack' => 'snack#index'

Once you’re done, you should be able to visit /admin/snack.json in your browser and you’ll see JSON for the snack! Our snack API seems to be working

Of course, as you build your feature to add more complexity you likely wouldn’t just return hardcoded JSON from a controller like this, you’d query the database and return it that way.

The Client Side (Ember.js)

If you open up your browser and visit /admin/snack (without the .json) you’ll see that Discourse says “Oops! That page doesn’t exist.” — that’s because there’s nothing in our front end Ember application to respond to the route. Let’s add a handlebars template to show our snack:

app/assets/javascripts/admin/templates/snack.hbs

{{model.name}}



{{model.description}}

And, like on the Rails API side we need to wire up the route. Open the file app/assets/javascripts/admin/routes/admin-route-map.js and look for the export default function() method. Add the following line:

this.route("snack");

We have one final thing left to do in Ember land, and that’s to have the Ember application perform an AJAX request to fetch our JSON from the server. Let’s create one last file. This will be an Ember Route. Its model() function will be called when the route is entered, so we’ll make our ajax call in there:

app/assets/javascripts/admin/routes/admin-snack.js

import { ajax } from "discourse/lib/ajax";

export default Ember.Route.extend({
  model() {
    return ajax("/admin/snack.json");
  },
});

Now, you can open your browser to /admin/snack and you should see the details of the snack rendered in the page!

Summary

Opening your browser to /admin/snack boots up the Ember application

The Ember application router says snack should be the route

The Ember.Route for snack makes an AJAX request to /admin/snack.json

The Rails application router says that should be the admin_snack controller

The admin_snack_controller returns JSON

The Ember application gets the JSON and renders the Handlebars template

Where to go from here

I’ve written a follow up tutorial on how to add an Ember Component to Discourse.

This document is version controlled - suggest changes on github.

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