[RUBY] When a beginner makes a personal app with rails, the procedure to bring it to the starting point anyway.


This time, I am writing an article assuming myself in the past who is thinking of making a web application for the first time using rails. After learning all the things, I understood "dots" to some extent about MVC, controllers, how to write methods, etc., but when I was working on "lines" called application production, my head was blank. I want to try various things, but I have to bring it to a working state for the time being. ** Anyway, it is a procedure to connect the routes and bring it to the point where the characters are displayed on the browser. ** ** From there, it is assumed that you will try and error what you want to do. You can do the same thing with scaffold, but I wanted to understand the flow and do it myself, so I'll explain it from the beginning.


ruby 2.6.5 rails


** When I hit localhost: 3000, "Hello new world!" Is displayed. ** **

Rough flow

  1. Decide what kind of app you want. ↓
  2. Creating a template ↓
  3. Development environment settings ↓
  4. Model setting / migration ↓
  5. Routing ↓
  6. Controller settings ↓
  7. Preparation of view

1 to 3 are tasks that can be completed only once when creating an application. (With exceptions) Images 4 to 7 are repeated as a set for each function. It does not have to be in this order.


1. Decide what kind of app you want.

Decide the purpose, name, function, page design, and DB design. I think it's difficult to design perfectly from the beginning, but I'll make it as clear as possible.

2. Creating a template

In the creation directory


rails _6.0.0_ new sample-app -d mysql

--Specify the rails version with _6.0_0_. --sample is the app name --You can specify the database with -d.

3. Initial setting setting


  encoding: utf8

Character code setting. At first, I think it is ʻencoding: utf8mb4, so change it. If it is not ʻutf8, an error may occur, so it is safe to change.


bundle install

If you have decided exactly what kind of GEM to put in step 1, it is better to put in GEM first.


rails db:create

Database creation. If you do not do this, the local server will not start.

4. Model setting / migration

You can reach your goal without doing step 4 this time.


rails g model book title:string author:string

This time, let's say you want to create a Book model with columns called title and author. Make the model name singular.


class CreateBooks < ActiveRecord::Migration[6.0]
  def change
    create_table :books do |t|
      t.string :title
      t.string :author


The numbers in 20200919134606_create_books will be different.


rails db:migrate

This command is for migration.

5. Routing


Rails.application.routes.draw do
  root to: 'books#index'
  resources :post, only: :index

The index of Books is set to the root (the page that is displayed by default when accessed. The top page). Upon access, the Books controller's index action will be called and views / books / index.html.erb will be displayed in the browser.


rails routes

With this command, you can check whether the described route has been established.

6. Create controller


rails g controller books index

Create a Books controller. This command also creates a view at the same time. Make the controller name plural.


class BooksController < ApplicationController
  def index

7. Preparation of view


<h2>Hello new world!</h2>

Write a description and start a local server.


rails s

Let's access [localhost: 3000](http: // localhost: 3000 /) on the browser. If it is displayed without error, it is successful. If you get an error, you have to read the contents carefully and deal with it.

in conclusion

For the time being, once you have reached this point, repeat the work of describing 4 to 7 in detail and creating it.

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