This guide is designed for beginners who want to get started with a Railsapplication from scratch. It does not assume that you have any prior experiencewith Rails. However, to get the most out of it, you need to have someprerequisites installed:
Rails is a web application framework running on the Ruby programming language.If you have no prior experience with Ruby, you will find a very steep learningcurve diving straight into Rails. There are several curated lists of online resourcesfor learning Ruby:
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Rails is a web application development framework written in the Ruby language.It is designed to make programming web applications easier by making assumptionsabout what every developer needs to get started. It allows you to write lesscode while accomplishing more than many other languages and frameworks.Experienced Rails developers also report that it makes web applicationdevelopment more fun.
Rails is opinionated software. It makes the assumption that there is a "best"way to do things, and it's designed to encourage that way - and in some cases todiscourage alternatives. If you learn "The Rails Way" you'll probably discover atremendous increase in productivity. If you persist in bringing old habits fromother languages to your Rails development, and trying to use patterns youlearned elsewhere, you may have a less happy experience.
By following along with this guide, you'll create a Rails project calledblog, a (very) simple weblog. Before you can start building the application,you need to make sure that you have Rails itself installed.
The examples below use $ to represent your terminal prompt in a UNIX-like OS,though it may have been customized to appear differently. If you are using Windows,your prompt will look something like c:\source_code>
Open up a command line prompt. On macOS open Terminal.app, on Windows choose"Run" from your Start menu and type 'cmd.exe'. Any commands prefaced with adollar sign $ should be run in the command line. Verify that you have acurrent version of Ruby installed:
A number of tools exist to help you quickly install Ruby and Rubyon Rails on your system. Windows users can use Rails Installer,while macOS users can use Tokaido.For more installation methods for most Operating Systems take a look atruby-lang.org.
Many popular UNIX-like OSes ship with an acceptable version of SQLite3.On Windows, if you installed Rails through Rails Installer, youalready have SQLite installed. Others can find installation instructionsat the SQLite3 website.Verify that it is correctly installed and in your PATH:
Rails comes with a number of scripts called generators that are designed to makeyour development life easier by creating everything that's necessary to startworking on a particular task. One of these is the new application generator,which will provide you with the foundation of a fresh Rails application so thatyou don't have to write it yourself.
If you're using Windows Subsystem for Linux then there are currently somelimitations on file system notifications that mean you should disable the springand listen gems which you can do by running rails new blog --skip-spring --skip-listen.
The blog directory has a number of auto-generated files and folders that makeup the structure of a Rails application. Most of the work in this tutorial willhappen in the app folder, but here's a basic rundown on the function of eachof the files and folders that Rails created by default:
Compiling CoffeeScript and JavaScript asset compression requires youhave a JavaScript runtime available on your system, in the absenceof a runtime you will see an execjs error during asset compilation.Usually macOS and Windows come with a JavaScript runtime installed.Rails adds the therubyracer gem to the generated Gemfile in acommented line for new apps and you can uncomment if you need it.therubyrhino is the recommended runtime for JRuby users and is added bydefault to the Gemfile in apps generated under JRuby. You can investigateall the supported runtimes at ExecJS.
This will fire up Puma, a web server distributed with Rails by default. To seeyour application in action, open a browser window and navigate to :3000. You should see the Rails default information page:
To stop the web server, hit Ctrl+C in the terminal window where it'srunning. To verify the server has stopped you should see your command promptcursor again. For most UNIX-like systems including macOS this will be adollar sign $. In development mode, Rails does not generally require you torestart the server; changes you make in files will be automatically picked up bythe server.
A controller's purpose is to receive specific requests for the application.Routing decides which controller receives which requests. Often, there is morethan one route to each controller, and different routes can be served bydifferent actions. Each action's purpose is to collect information to provideit to a view.
A view's purpose is to display this information in a human readable format. Animportant distinction to make is that it is the controller, not the view,where information is collected. The view should just display that information.By default, view templates are written in a language called eRuby (EmbeddedRuby) which is processed by the request cycle in Rails before being sent to theuser.
Now that we have made the controller and view, we need to tell Rails when wewant "Hello, Rails!" to show up. In our case, we want it to show up when wenavigate to the root URL of our site, :3000. At the moment,"Welcome aboard" is occupying that spot.
This is your application's routing file which holds entries in a specialDSL (domain-specific language)that tells Rails how to connect incoming requests tocontrollers and actions.Edit this file by adding the line of code root 'welcome#index'.It should look something like the following:
root 'welcome#index' tells Rails to map requests to the root of theapplication to the welcome controller's index action and get 'welcome/index'tells Rails to map requests to :3000/welcome/index to thewelcome controller's index action. This was created earlier when you ran thecontroller generator (bin/rails generate controller Welcome index).
Launch the web server again if you stopped it to generate the controller (bin/railsserver) and navigate to :3000 in your browser. You'll see the"Hello, Rails!" message you put into app/views/welcome/index.html.erb,indicating that this new route is indeed going to WelcomeController's indexaction and is rendering the view correctly.
In the Blog application, you will now create a new resource. A resource is theterm used for a collection of similar objects, such as articles, people oranimals.You can create, read, update and destroy items for a resource and theseoperations are referred to as CRUD operations.
If you run bin/rails routes, you'll see that it has defined routes for all thestandard RESTful actions. The meaning of the prefix column (and other columns)will be seen later, but for now notice that Rails has inferred thesingular form article and makes meaningful use of the distinction.
In the next section, you will add the ability to create new articles in yourapplication and be able to view them. This is the "C" and the "R" from CRUD:create and read. The form for doing this will look like this:
Firstly, you need a place within the application to create a new article. Agreat place for that would be at /articles/new. With the route alreadydefined, requests can now be made to /articles/new in the application.Navigate to :3000/articles/new and you'll see a routingerror:
This error occurs because the route needs to have a controller defined in orderto serve the request. The solution to this particular problem is simple: createa controller called ArticlesController. You can do this by running thiscommand:
A controller is simply a class that is defined to inherit fromApplicationController.It's inside this class that you'll define methods that will become the actionsfor this controller. These actions will perform CRUD operations on the articleswithin our system.
This error indicates that Rails cannot find the new action inside theArticlesController that you just generated. This is because when controllersare generated in Rails they are empty by default, unless you tell ityour desired actions during the generation process.
To manually define an action inside a controller, all you need to do is todefine a new method inside the controller. Openapp/controllers/articles_controller.rb and inside the ArticlesControllerclass, define the new method so that your controller now looks like this:
The first part identifies which template is missing. In this case, it's thearticles/new template. Rails will first look for this template. If not found,then it will attempt to load a template called application/new. It looks forone here because the ArticlesController inherits from ApplicationController.
The next part of the message contains request.formats which specifiesthe format of template to be served in response. It is set to text/html as werequested this page via browser, so Rails is looking for an HTML template.request.variant specifies what kind of physical devices would be served bythe response and helps Rails determine which template to use in the response.It is empty because no information has been provided.
The simplest template that would work in this case would be one located atapp/views/articles/new.html.erb. The extension of this file name is important:the first extension is the format of the template, and the second extensionis the handler that will be used to render the template. Rails is attemptingto find a template called articles/new within app/views for theapplication. The format for this template can only be html and the defaulthandler for HTML is erb. Rails uses other handlers for other formats.builder handler is used to build XML templates and coffee handler usesCoffeeScript to build JavaScript templates. Since you want to create a newHTML form, you will be using the ERB language which is designed to embed Rubyin HTML. 152ee80cbc
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