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6 CHAPTER 1 Ruby on Rails, the framework
Next, you need to install the rails gem. The following command installs both
Rails and its dependencies. If you’re using the Rails installer you will not need to run
this command because Rails will already be installed:
gem install rails -v 3.1.0
1.2.2 Generating an application
With Rails now installed, to generate an application, you run the rails command and
pass it the new argument and the name of the application you want to generate:
things_i_bought. When you run this command, it creates a new directory called
things_i_bought, which is where all your application’s code will go. You can call your
application anything you wish, but it can’t be given the same name as a reserved word
in Rails. For example, you wouldn’t call your application rails because it defines a Rails
constant, which is internal to Rails, and the two constants would clash.
The application that you’re going to generate will be able to record purchases you
have made. You can generate it using this command:
rails new things_i_bought
The output from this command may seem a bit overwhelming at first, but rest assured:
it’s for your own good. All of the directories and files generated here provide the
building blocks for your application, and you’ll get to know each of them as we progress.
For now, let’s get rolling and learn by doing, which is the best way of learning.
1.2.3 Starting the application
To get the server running, you must first change into the newly created application’s
directory and then run these commands to start the application server:
cd things_i_bought
bundle install
rails server
The bundle install command installs all the gems required for your application.
This is explained in further detail in chapter 3.
This starts a web server on your local address on port 3000 using a Ruby standard
library web server known as WEBrick. It will say it’s “starting in development on
http://0.0.0.0:3000,” which indicates to you that the server will be available on port
3000 on all network interfaces of this machine. 8 To connect to this server, go to
http://localhost:3000 in your favorite browser. You’ll see the “Welcome aboard”
page, which is so famous in Rails (see figure 1.1).
If you click About Your Application’s Environment, you’ll find your Ruby, Ruby-
Gems, Ruby on Rails, and Rack versions and other environmental data. One of the
things to note here is that the output for Environment is Development. Rails provides
8 This is what the 0.0.0.0 address represents. It is not an actual address, so to speak, and so localhost or
127.0.0.1 should be used.