[RUBY] Use CarrierWave to set a user's profile picture

procedure

1. Add Gemfile

gem 'carrierwave'

$ bundle install

2. Generate Uploader

uploaders / image_uploader.rb is generated.

$ rails g uploader image

3. Edit model

Set to use uploader in user.rb.

models/user.rb

class User < ApplicationRecord
  mount_uploader :image, ImageUploader
end

4. Edit view

new.html

<%= form_with(model: user, local: true) do |form| %>
  <%= form.text_field :name %>
  <%= form.email_field :email %>
  <%= form.password_field :password %>
  <%= form.file_field :image %>
 　#Image file information_Let's add the following sentence to temporarily save it in the cache!
  <%= form.hidden_field :image_cache %>
  <%= form.submit %>
<% end %>

index.html

//The image image can be displayed with the following description//
<%= image_tag @user.image.url %>

//When conditional branching with if statement//
<% if @user.image? %>
  <%= image_tag @user.image.url %>
<% else %>
  #If you want to display by default
  <%= image_tag "/assets/default.jpg " %>
<% end %>

5. Minimagic introduction

gem 'mini_magick'

$ bundle install

6. Edit the image_uploader.rb file

image_uploader.rb

class AvaterUploader < CarrierWave::Uploader::Base

　　include CarrierWave::MiniMagick 
　　#Resize image
　　process resize_to_fit: [100, 100]
end 

that's all