A simple example on usage of go-on-rails generator

This is an simple example for the go-on-rails, a Rails generator.

You can take the example as a tutorial, too. I'll make it as simple and clear as possible to show how to use the go-on-rails generator to generate Golang codes in a Rails app.

Even though I highly recommend you to get a quick overview of go-on-rails to learn some commands usage before taking further in this example.

Environments

• macOS Sierra v10.12.4
• Ruby v2.6.3
• Rails v5.0.2
• MySQL v5.7.11
• Golang v1.12.6 darwin/amd64

Build a Rails app

Firstly, we will follow the tutorial in Rails guides, to build a (very) simple weblog. We may not copy that whole steps, but the models mainly.

Let's create a new Rails app:

rails new example_simple --api --database mysql --skip-bundle

change to the new directory, add the gem go-on-rails:

# edit Gemfile
gem 'go-on-rails', '~> 0.4.0'

and then bundle:

bundle install

Create some models

We'll build two models: Article and Comment. And there's a has_many association between them.

rails g model Article title:string text:text

rails g model Comment commenter:string body:text article_id:integer

You'd better add some restrictions to the migration files to give a limit on database level, eg. add null: false to the title column:

# the migration file under db/migrate
class CreateArticles < ActiveRecord::Migration[5.0]
  def change
    create_table :articles do |t|
      t.string :title, null: false
      t.text :text

      t.timestamps
    end
  end
end

And meanwhile we add some presence and length validations to the models:

# app/models/article.rb
class Article < ApplicationRecord
  has_many :comments, dependent: :destroy

  validates :title, presence: true, length: { in: 10..30 }
  validates :text, presence: true, length: { minimum: 20 }
end

# app/models/comment.rb
class Comment < ApplicationRecord
  belongs_to :article

  validates :commenter, presence: true
  validates :body, presence: true, length: { minimum: 20 }
end

Then run the migration:

rails db:migrate

Generate Golang codes

Now it's time to show magic!

Run the command:

rails g gor dev

and a new directory named go_app with some files will be created under the root of Rails app:

# directory structure of go_app

├── controllers
│   └── home_controller.go
├── main.go
├── models
│   ├── db.go
│   ├── gor_article.go
│   └── gor_comment.go
├── public
│   └── favicon.ico
└── views
    └── index.tmpl

then let's install Golang dependancies(some packages) we'll use:

rails gor:deps

when the installation completed after some while, make sure you now under the root of go_app and run:

go run main.go

open http://localhost:4000 by default in your browser, you can see a welcome page from go-on-rails:

What on earth be generated?

public

The dir serves the static assets. You can create new directories or files under public, or you can create any other directories under the go_app, and then set the routes for serve the file system. How to set it

models

• Each file here heading with gor_ corresponding to each model we created by the rails g model command above, all functions are mostly for database CRUD manipulations, and also some basic validations and associated operations
• You can create new .go files to add more functions for the models under the models directory using the package name model
• You can view the godoc page of all functions in http://localhost:7979/doc/models.html after run:

rails gor:doc

controllers

• Now only a controllers directory and a home_controller are generated by default
• Under the controllers directory we can create handlers for the HTTP routes we set in the main.go file, we call them controllers by the Rails convention
• For the structure clearity we create one controller file corresponding to each model like Rails does, too

views

• yes, you can put all the template files here
• Because we choose the Gin HTTP framework, we can load all the templates in at initial time See how to config it

Let's go on our example

In this simple example we just build APIs interacting with data in JSON format.

Create some customed controllers

• We create articles_controller.go and comments_controller.go for each model. Each function to a RESTful action.
• Import model package to use avaliable functions and methods we have generated

Add routes for the controller functions

In the main.go add some routes to map the HTTP requests to the right handlers we created in the controller files.

// for the articles
r.GET("/", c.HomeHandler)
r.GET("/articles", c.ArticlesIndex)
r.POST("/articles", c.ArticlesCreate)
r.GET("/articles/:id", c.ArticlesShow)
r.DELETE("/articles/:id", c.ArticlesDestroy)
r.PUT("/articles/:id", c.ArticlesUpdate)

Testing with curl command

In a terminal window run go run main.go, in another terminal use curl command to test API we added.

For example, to get all article records:

curl -XGET 'http://localhost:4000/articles'

To create a new article, run:

curl -XPOST 'http://localhost:4000/articles' -d '{ "title": "Use go-on-rails to build a Golang app", "text": "blablabla..." }'

You can check the main.go and controller files in this repository for details.