Add the following to the bottom of the .gitignore file.

.gitignore

/.env

Creating a controller

Terminal

$ rails g controller contacts

app/controllers/contacts_controller.rb

class Public::ContactsController < ApplicationController
  def new
    @contact = Contact.new
  end
  
  #If you want to create a confirmation screen, you should write something like this.
  #Receive input from new action
  #When the submit button is pressed, the create action is executed.
  def confirm
    @contact = Contact.new(contact_params)
    if @contact.invalid?
      render :new
    end
  end
　
  #If there is an error in the input contents,
  #I think it is natural to return to the previous page while retaining the input contents,
  #This is possible by defining a back action.
  def back
    @contact = Contact.new(contact_params)
    render :new
  end

  #It is the action that is actually sent.
  #This is the first time you save your input.
  #For security reasons, you may want to delete the input contents after a certain period of time.
  def create
    @contact = Contact.new(contact_params)
    if @contact.save
      ContactMailer.send_mail(@contact).deliver_now
      redirect_to done_path
    else
      render :new
    end
  end

  #Please use when using the transmission completion screen.
  def done
  end

  private

  def contact_params
    params.require(:contact)
          .permit(:email,
                  :name,
                  :phone_number,
                  :subject,
                  :message
                 )
  end
end

routing edit

config/routes

resources :contacts, only: [:new, :create]
post 'contacts/confirm', to: 'contacts#confirm', as: 'confirm'
post 'contacts/back', to: 'contacts#back', as: 'back'
get 'done', to: 'contacts#done', as: 'done'

edit view

Under app / views / contact_mailer send_mail.html.erb Please create send_text.html.erb.

• I don't know why I will create two, so I would like to entrust it to myself in the future. .. .. Please fill in the same content

erb:app/views/contact_mailer/send_mail.html.erb,send_text.html.erb

<%= @contact.name %>I received an inquiry from Mr.<br>
【Tel】：<%= @contact.phone_number %><br>
【Mail】：<%= @contact.email %><br>
[Requirements]:<%= @contact.subject_i18n %><br>
【Content of inquiry】<br>
<span style="white-space: pre-wrap;"><%= @contact.message %></span>

We will create the actual input form.

• Describe only the name and message.

erb:app/views/contacts/new.html.erb

<%= form_for(@contact, url: confirm_path) do |f| %>
  <div class="form-group">
    <%= f.label :name, 'name*' %>
    <%= f.text_field :name, autofocus: true, class: 'form-control' %>
  </div>
    
  <div class="form-group">
    <%= f.label :message, 'message*' %>
    <%= f.text_area :message, size: '10x10', class: 'form-control' %>
  </div>

  <div>
    <%= f.submit 'Confirm input' %>
  </div>
<% end %>

Write the code to return to the input screen from the confirmation screen.

• Describe only the name and message.

erb:app/views/contacts/confirm.html.erb

<table>
  <tbody>
    <tr>
      <td class="text-center" style="width: 30%;">name</td>
      <td><%= @contact.name %></td>
    </tr>
    <tr>
      <td class="text-center">message</td>
      <td style="white-space: pre-wrap;"><%= @contact.message %></td>
    </tr>
  </tbody>
</table>

<%= form_for(@contact) do |f| %>
  <%= f.hidden_field :name %>
  <%= f.hidden_field :email %>
  <%= f.hidden_field :phone_number %>
  <%= f.hidden_field :subject %>
  <%= f.hidden_field :message %>
  <div><%= f.submit 'Send' %></div>
<% end %>
<%= form_for @contact, url: back_path do |f| %>
  <%= f.hidden_field :name %>
  <%= f.hidden_field :email %>
  <%= f.hidden_field :phone_number %>
  <%= f.hidden_field :subject %>
  <%= f.hidden_field :message %>
  <div><%= f.submit 'Returns to the input screen' %></div>
<% end %>