Tutorial: Create a real-time web game with Django Channels and React

The Lobby Page…with React

If you’re unfamiliar with React, it’s essentially a front-end library that acts as the “view” layer for web applications (and native mobile with React Native). With it, developers can create components that can manage their own state, actions and UI elements. Combining small React components together can allow you to build fast, reactive, yet complex user interfaces. Using React with Django isn’t as straightforward as just using the standard Django templates with a little javascript, though. We’ll need to bring in a few libraries and tools to get the job done.

Node – NPM

We’ll start with Node and it’s package manager, npm. If you’ve only worked with Django in the past, you may not have had a chance to play with npm. It can be compared to pip in some ways, as it installs the requested versions of libraries and frameworks. Similar to the requirements.txt file that is commonly used to track and install python packages in pip, npm uses a packages.json file in much the same way.

If you’re not sure if you have Node and npm installed, you can check the versions with in your terminal by running  node -v (should be at least v0.10.32)and  npm -v  (should be at least v2.1.8). If you don’t have either of these, you can get the installation info here.

So, once you have confirmed that you have those and they’re relatively up-to-date, let’s move on to create the package.json file in our project.

In your terminal, at the root of the project, type:

 

Just accept the defaults for now and then you should have a shiny new package.json file. Next, we’ll install a few packages:

• React
• Webpack – packages up all of the React JSX files into a single file in browser-readable JS format.
• Babel – Used by webpack and does the actual converting of the JSX to JS
• Babel-Loader – webpack plugin to allow Babel
• React-Websocket – Websockets made easy for React
• Babel Presets: presets for es2015 and React

In your terminal:

With webpack installed now, we need to create config file. Create a webpack.config.js file in the root of your project (same directory as manage.py). Add the following to that file:

What we’ve added there are the instructions for what webpack should do when run. Key bits to note there are:

• Line 9-11: We’re telling it that we want a “lobby” bundle to be created from the JS and JSX files that will soon be in the url we’ve provided.
• Line 12-15: This is setting where we want the bundle to be created and how to name it.
• Line 25-36: This is the array (with only one item) that specifies the loader we’ll be using with webpack. We’re using babel, telling it to exclude files in node_modules, and the presets so babel know’s what type of files its processing.

Lobby Template and React Components

React is a flexible library when it comes to how you structure your project. Many devs will create a react component from which all other components are rendered, so the entire project has a single entry point. This works really well for single page applications (SPAs) for obvious reasons. In Django, this pattern doesn’t really fit because Django is all about having multiple pages being served up by their specific URL & View. So, we’re going to keep using that pattern: URL -> VIEW -> TEMPLATE, but we’ll then have the template load the React components it needs.

If you refer back to line 10 in webpack.config.js, you’ll see that we’re specifying our first bundle – lobby. We want to include all of our lobby front-end code in that location, which will include the Django html template that is loaded from the view we already created. That directory will additionally hold to all of the React component files that are lobby specific.

So, webpack will pack all of those lobby JSX into a single JS bundle file we can use. To easily choose the bundle we want to work with in a particular Django template, we can use the django-webpack-loader project. Let’s add that now:

And add ‘webpack_loader’ to your INSTALLED_APPS (settings.py) after ‘channels’ in addition to some settings for the loader:

 

Create a components directory inside templates. Inside it, create a lobby directory. In that directory, create the Django template file lobby.html. Your templates folder should now look like this:

Now, fill the new lobby.html file with this code:

If you’ve worked with Django before, this all should look very standard. Some things to note:

• Line 2: Loading the render_bundle template tag from the webpack_loader Django app we installed earlier.
• Line 7: Using that tag to drop the lobby bundled up JS that webpack will create.
• Line 12: Regular old Django… React is just supplementing the template, we can always just use standard Django template features around those components.
• Line 14: The div element that React will fill with the components.

That’s it for our lobby component’s root template. Now, we’re going to work with React.

Again looking at line 10 in the webpack.config.js file, you’ll see that the lobby bundle entry points to an index file. Each component folder and bundle needs this entry file, which handles the React imports and then renders the main component into the lobby_component div. This file also will be our first .jsx file.

JSX?

JSX, a React syntax that extends Javascript, is what most devs use when working with React. JS would work just fine, but you get additional benefits with JSX including: ES6 features and syntax and, most importantly, the ability to cleanly embed HTML directly in the script. It looks odd the first time you see it, but it really makes component building clean and easy.

Create the index.jsx file in the lobby directory.

While not a React component, we still used JSX syntax to take advantage of those features we mentioned above. Lines of note:

• Lines 1-4: ES6 imports instead of Node’s require for module importing
• Line 7: Websock url we’ll use to connect to the Channels lobby route we created earlier
• Line 9: Default the current_user to null until we do something to retrieve that a little later
• Line 12-14: Our first bit of React syntax. ReactDOM.render will render the base component on the page.
• Line 18: Calls the function that renders the component.

Let’s take a look at that what that line is rendering:

This is the React syntax to display a component. The component must be imported into the current context, which we did on line 2. This syntax should be familiar as it’s basically just HTML with a tag name (the component) and attributes which are React props. You can think of React components as Javascript functions that take in parameters – the props. So the syntax above is a HTML-ish way to call the LobbyBase function, passing current_user and socket as parameters.

The {current_user} and {lobby_sock} look similar to the double curly braces of Django template variables, but in React the single curly braces allow you to embed javascript expressions or variables.

Lobby Base Component

Create a LobbyBase.jsx file in the lobby directory and add this as its content:

There’s a lot there, so let’s break down this into pieces…

At the top, we’re importing our React component, including two we will create in a moment.

The above line shows how to define a component as an ES6 class. There is also a createClass method for ES5. Check out this excellent article for the differences, if you’re interested. In this case, we’ll go ES6.

 

The constructor method runs when the component is instantiated. Typically, this is where you handle defaulting state from the props in React.

State is very much like props in React, but it is local to, and controlled by, the component. State should hold data that can change in the component, not static values.

We’ll discuss state a little more later, but for now just note that we’ll default the state values in the constructor.

But the constructor is also useful for binding the class methods to this, the class instance. You’ll see this on line 16: this.sendSocketMessage = this.sendSocketMessage.bind(this) Here we’re binding the instance method sendSocketMessage to the class instance, this. This isn’t JSX specific, but just how Javascript works. To avoid manual binding, you could use the ES5 createClass method to build your components. The binding is automatic using that method.

The React team recommends using the constructor as the spot to do your binding. This ensures that binding won’t unnecessarily run multiple times. But you don’t have to bind there, and as I’ll do often in this tutorial, I’ll break from the recommended to show other ways to achieve things on purpose. If you take a look at Line 45, you’ll see we bind this to a class method.

Speaking of class methods, you’ll see there are several in our component’s class alongside a couple of custom methods. React has “lifecycle methods” that we can use to tap into spots of the component’s lifecycle, just as we did with the contructor. The others we use in this component are: 

• componentDidMount – invoked immediately before mounting occurs and it runs before render
• componentWillUnmount – not invoked when first instantiated, but will be immediately after the component is updated.
• render – a required method, returns the component

The custom methods we have currently are: sendSocketMessage and handleData. These are our handlers for sending and receiving messages over the websocket, which you can see will be rendered by the render method as a React component.

Also, you’ll find below the class that we’re setting a propTypes property on the component class. This helps with type-checking to ensure that the props coming in are the types expected by the component. Our only prop we’ve defined here is the socket url, which needs to be a string.

And finally, we’re exporting the module at the bottom of the file, which allows it to be imported in index.jsx

Webpack It Up

Webpack is now configured to look at our lobby component directory, pack up those files into a bundle and deliver it to our static files directory. We now have files to pack in that folder, so let’s do that now with:

If all goes well, you should have some details of the webpack run in your terminal with no errors. You should also now see a file in your /static/bundles/ directory. If you’re interested, view the contents of this file and you’ll see how Webpack and babel put it all together.

Watch Mode – a nice feature of webpack is the watch mode you can trigger. This will allow webpack to continually watch for changes in any of your entry folders and compile on the fly. To do this, add  --watch  at the end of the command we ran above. If you don’t use –watch, you’ll need to manually run the command each time you make a change to any JSX file.

If everything goes well with webpack, run your project again with:  python manage.py runserver 8080 and then log into your app. If it doesn’t send you to the lobby page, you can click “Lobby” in the top menu. If everything worked, you should see something like:

Here you can see the mix of Django template and React: The template (lobby.html) renders out the “Let’s play…” line using the {{request.user.username}} from Django. Under that, you’ll see the “Lobby Components will go here…” line, which you’ll find in your LobbyBase component.

Note: You will need to be logged in to see the lobby.

Next we’ll add in some real functionality to our lobby…