Scaffold Application with Docker + Ruby on Rails!

Prerequistics

1. Docker installed in PC
2. Ruby and Rails installed in PC

Premise in windwons

1. WSL2 / Ubuntu / Docker Desktop must be installed * Click here for the procedure

Procedure

---

File preparation

1. Launch Docker Desktop

2. Start powershell or termical

3. Create a D: \ docker \ test-app directory

   In Mac or ubuntu or linux

   mkdir docter/test-app

   in Windows

   make directory manually docket\test-app

4. Change to the test-app directory

cd D:\docker\test-app

1. Create a Dockerfile

D:\docker\test-app\Dockerfile

Describe the following in the Dockerfile

FROM ruby:2.3.3
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs
RUN mkdir /myapp
WORKDIR /myapp
ADD Gemfile /myapp/Gemfile
ADD Gemfile.lock /myapp/Gemfile.lock
RUN bundle install
ADD . /myapp

1. Create a Gemfile

D:\docker\test-app\Gemfile

Describe the following in the Gemfile

source 'https://rubygems.org'
gem 'rails', '5.0.0.1'

1. Create Gemfile.lock (empty file)

D:\docker\test-app\Gemfile.lock

1. Create a data folder

D:\docker\test-app\data

1. Create docker-compose.yml

D:\docker\test-app\docker-compose.yml

Describe the following in docker-compose.yml

version: '3'
services:
  db:
    image: postgres
    volumes:
      - ./data:/var/lib/postgresql/data
    environment:
      POSTGRES_DB: "db"
      POSTGRES_HOST_AUTH_METHOD: "trust"
  web:
    build: .
    command: /bin/sh -c "rm -f /myapp/tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    volumes:
      - .:/myapp
    ports:
      - "3000:3000"
    depends_on:
      - db

App creation + settings

---

Hinagata app creation

docker-compose run web rails new . --force --database=postgresql

1. Rebuild the image

docker-compose build

1. Rewrite config / database.yml

default: &default
  adapter: postgresql
  encoding: unicode
  host: db
  username: postgres
  password:
  pool: 5

development:
  <<: *default
  database: myapp_development

test:
  <<: *default
  database: myapp_test

1. Launch the app

docker-compose up

1. Create DB * Start and execute powershell separately from running

docker-compose run web rake db:create

1. Execute scaffold * Start and execute powershell separately from running

docker-compose run web bin/rails g scaffold User name:string

1. Apply migration * Start and execute powershell separately from running

docker-compose run web bin/rails db:migrate

1. Confirmation

Access the site with a browser and check

http://localhost:3000

Error handling

---

• If “Gem :: InstallError: XXXX requires Ruby version” appears when you execute the command in the terminal 　→ Sorry to trouble you, but let’s delete the test-app created this time and start over. 　　In step 6 of file preparation, set the ruby ​​version in the Dockerfile to 2.4.0 .

　 　FROM ruby:2.4.0

• If you run http: // localhost: 3000 in your browser and get a Rails error of “key must be 32 bytes” 　→ Sorry to trouble you, but let’s delete the test-app created this time and start over….

　　In step 7 of file preparation, set the Rails version in Gemfile to 5.0.1 .

　 　gem 'rails', '5.0.1'

Reference article

Docs.docker.jp

qiita.com

Happy Coding :)