Rails CRUD function implementation ① (new addition, deletion this time)

Purpose of this article It is a procedure to create a web application with CRUD function using rails. It is a site (bird tweet) where you can post pictures and names of birds.

Creating a rails application

Specify version 6.0.0 of rails. Specify the DB (mysql in this case) to be used after -d.

rails _6.0.0_ new birdtweet -d mysql

setting change.


#  encoding: utf8mb4
  encoding: utf8

DB creation

cd birdtweet
rails db:create

Editing Gemfile Open the Gemfile directly under the project


# gem 'mysql2', '>= 0.4.4'
gem 'mysql2', '>= 0.5.3'
(Bottom line of file)
gem 'pry-rails'

Update settings in the terminal

bundle update

Creating a model At the terminal
rails g model bird

Add column


create_table :birds do |t|
      t.string :name
      t.text :pic

Update your changes with commands!

rails db:migrate

Put some data in the DB at the console.

rails c
Bird.create(name: "Puffin", pic: "https://cdn.pixabay.com/photo/2020/05/26/13/22/puffins-5223057_1280.jpg ")
Bird.create(name: "Kingfisher", pic: "https://cdn.pixabay.com/photo/2017/02/07/16/47/kingfisher-2046453_1280.jpg ")

Creating a controller Create a controller with the following command.
rails g controller birds

Pluralized or not, confusing, Only the model is singular!

Flow from here The flow of creating each function is almost the same!

Added to routes.rb ↓ Added links to each function in index.html.erb (unexpected index) ↓ Added to birds_controller.rb ↓ Function name.html.erb creation

List display function Rails has 7 actions.
  • index: List
  • show: Details
  • new: Transition to new creation screen
  • create: Save new data
  • edit: Transition to edit screen
  • update: Update edits
  • destroy: Delete

If you do not want to use all the functions, specify only the ones to be used with the only option.


#Behind resources is the plural of the model name
  resources :birds, only: :index


def index
    #Store the Bird model data in an instance variable.
    @birds = Bird.all

index.html.erb file creation Display all instance variables in the view using the each method.


<% @birds.each do |bird| %>
<%= bird.name %>
<div style=
"background-image: url(<%= bird.pic %>); 
 background-position: center center;
 background-size: cover;
 width: 300px; 
 height: 300px;
 margin-bottom: 10px;

It was displayed as below! !! !! image.png

New posting function The flow is also routes → controller → view, but since data is added (create) from moving to the posting screen (new), we will do a series of flows twice!


Rails.application.routes.draw do
  #Behind resources is the plural of the model name
  #If there are multiple actions, I will make it in the form of an array
  resources :birds, only: [:index, :new]


<%=link_to 'New post', new_bird_path, method: :get%>



def new
  #Store the instantiated version of the Bird model in an instance variable.
  @bird = Bird.new

Create new.html.erb


<%#Even if you do not describe the transition destination url, it will transition based on the model put in the instance variable.%>
<%=form_with(model: @bird, local: true) do |form| %>
  <%= form.text_field :name, placeholder: "Bird name" %>
  <%= form.text_field :pic, placeholder: "Bird photo URL" %>
  <%= form.submit "Post" %>

http://localhost:3000/birds/new You can see the posting screen when you access! image.png

Next is the function to register the input information.


Rails.application.routes.draw do
  #Behind resources is the plural of the model name
  #If there are multiple actions, I will make it in the form of an array
  resources :birds, only: [:index, :new, :create]

birds_controller.rb The data will be sent in the form of a hash from the form.
It is dangerous to receive all the data! </ b>
Even though only the name and URL of the photo are required, the login information key can be maliciously added, and the login information of another person can be changed and hijacked without permission. So we use strong parameters.
Also, below the line that describes private, it is a method that cannot be called from other files. The advantage is that you can see fewer files when you have more methods.


  def create
    #bird defined under private_Receives the parameter specified by param and saves it.

  def bird_param
    # params.require(:Model name).permit(:Column name,:Column name,......)
    params.require(:bird).permit(:name, :pic)

create.html.erb create


<h3>Posting completed!</h3>
<a href="/birds">To List</a>



If you leave it as it is, you will be able to register without entering anything. Therefore, I will write a description for validation check.


class Bird < ApplicationRecord
  #Write the column name you want to be required to enter.
  validates :name, presence: true
  validates :pic, presence: true

You can no longer register the data from now on! !!

Delete function


resources :birds, only: [:index, :new, :create, :destroy]

To find the link to the delete function, first use the command.

rails routes

will do. Then, the following output will be output. If you add "_path" to the Prefix value, the URL described in the URI will be output. image.png

This time it's deleted, so pay attention to the line that says DELETE in the verb. Prefix is "bird", so you can set it to "bird_path". The method is "DELETE" in "Verb", so you can just say "delete". After that, pass the id as well!


<%= bird.name %><%=link_to "Delete", bird_path(bird.id), method: :delete%>

The link is displayed. image.png


  def destroy
    #This time I will not send the extracted data anywhere, [email protected] not attach.
    bird = Bird.find(params[:id])


<a href="/birds">List screen</a>

image.png image.png Puffin has been removed properly!

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