[Introduction] Try to create a Ruby on Rails application

Introduction

I just made my debut in Ruby on Rails at work the other day. When it comes to Rails, I had the impression that a Web service with screen display was created, but at work, the API was created with Rails. So, here I will try both creating a web service and an API.

environment

Windows 10 Home 64-bit

• For environment construction, see "Ruby on Rails installation (Windows10)".

How Rails works

Rails works with a mechanism based on the MVC model. MVC comes from the acronyms "Model", "View", and "Controller", respectively, and often appears when developing applications with Rails.

• For details on MVC, see "Ruby on Rails --MVC Model and REST Architecture".

Web service creation

Create a web screen that displays the "Hello World" that is customary for beginners.

1. 1. Create a new project

Execute the following command to create a new project for the web service.

Command line

rails new application name

* About folder structure

The folder structure under the application folder is in Rails Documents. You can check it in "What is Ruby on Rails> Folder structure> Folder list".

2. Creating a controller

Run the following command to create the controller. When creating a controller, move to the application folder created earlier and then create it.

Command line

cd application folder
rails generate controller controller name

The controller "hello_world_controller.rb" has been created under the "app / controllers" folder. The source code at the time of generation is as follows.

hello_world_controller.rb

class HelloWorldController < ApplicationController
end

3. 3. Creating an action

The methods defined in the controller are called actions. Edit the "hello_world_controller.rb" created earlier and try to define the "index" action.

hello_world_controller.rb

class HelloWorldController < ApplicationController
  def index
  end
end

* Batch creation of controller and action

The controller and action were created separately here, but it is also possible to create them all at once when creating the controller. To create all at once, execute the following command.

Command line

rails generate controller controller name action name 1 action name 2...

#Example
rails generate controller hoge index create

4. Add view

Under the "app / views / hello_world" folder, add the view "index.html.erb" corresponding to the index action.

• If nothing is described in the action, it is linked to "app / view / controller name / action name.html.erb" by default.

Since it is assumed that "Hello World" will be displayed this time, describe as follows in "index.html.erb".

html:index.html.erb

<h1>Hello World</h1>

5. Add routing settings

Receive the request from the browser and add the setting to distribute to the controller. The file to be modified is "routes.rb" under the "config" folder.

routes.rb

Rails.application.routes.draw do
  # For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
  get '/helloworld', to: 'hello_world#index'
end

You can check the format in "Routing Definition" in Rails Document. This time, I described the get method corresponding to the GET request.

6. Start Rails server

Run the following command to start the Rails server.

Command line

rails s

7. Check the operation from the browser

Go to http: // localhost: 3000 / helloworld.

• "Hello world" in the URL is the part of'/ hello world' defined by get in "routes.rb". "Hello World" is displayed safely!

API creation

Create an API that returns "Hello World" in JSON format. The general flow is the same as for Web services.

1. 1. Create a new project

Execute the following command to create a new API project. Add --api to a normal command and create a project in API mode.

Command line

rails new application name--api

2. Creating controllers and actions

The execution command is the same as the Web service. This time, let's create a controller and an action at once. The controller name and action name are the same as for the Web service. You can see the effect of API mode when creating a project here. If you create a controller normally, files related to views such as view, helper, and asset will be created at the same time, but those files will not be created because the API does not require views.

3. 3. Edit controller

Add a process to return "Hello World" in JSON format.

hello_world_controller.rb

class HelloWorldController < ApplicationController
  def index
    render json: { data: "Hello World" }
  end
end

4. Change routing settings

Since the controller and action were created at once, the routing settings are automatically added, but I will change them.

Change before_routes.rb

Rails.application.routes.draw do
  get 'hello_world/index'
  # For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
end

After change_routes.rb

Rails.application.routes.draw do
  get '/helloworld', to: 'hello_world#index'
  # For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
end

5. Start Rails server

Run the following command to start the Rails server.

• Since a Web service project is also created in parallel, start the server on a port different from the default port.

Command line

rails s -p 3001

6. Execute the curl command and check the operation

Execute the following command and confirm that JSON is returned.

Command line

curl --request GET --url http://localhost:3001/helloworld