[RUBY] [Rails] How to upload multiple images using Carrierwave



Development environment

・ Ruby: 2.5.7 Rails: 5.2.4 ・ Vagrant: 2.2.7 -VirtualBox: 6.1 ・ OS: macOS Catalina


The following has been implemented.

Slim introduction -Login function implementationImplementation of posting function


1. Introduce Gem


gem 'carrierwave'
gem 'mini_magick'

gem 'mini_magick' ➡︎ Allows you to change the size of the image when uploading.


$ bundle

2. Create an image setting file


$ rails g uploader image

ʻThe following file is created in app / uploaders / image_uploader.rb`. The setting method will be explained later.


class ImageUploader < CarrierWave::Uploader::Base
  # Include RMagick or MiniMagick support:
  # include CarrierWave::RMagick
  # include CarrierWave::MiniMagick

  # Choose what kind of storage to use for this uploader:
  storage :file
  # storage :fog

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir

  # Provide a default URL as a default if there hasn't been a file uploaded:
  # def default_url(*args)
  #   # For Rails 3.1+ asset pipeline compatibility:
  #   # ActionController::Base.helpers.asset_path("fallback/" + [version_name, "default.png "].compact.join('_'))
  #   "/images/fallback/" + [version_name, "default.png "].compact.join('_')
  # end

  # Process files as they are uploaded:
  # process scale: [200, 300]
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
  # version :thumb do
  #   process resize_to_fit: [50, 50]
  # end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
  # def extension_whitelist
  #   %w(jpg jpeg gif png)
  # end

  # Override the filename of the uploaded files:
  # Avoid using model.id or version_name here, see uploader/store.rb for details.
  # def filename
  #   "something.jpg " if original_filename
  # end

3. Add column


$ rails g migration AddImagesToBooks images:json


$ rails db:migrate


create_table "books", force: :cascade do |t|
  t.integer "user_id"
  t.string "title"
  t.text "body"
  t.datetime "created_at", null: false
  t.datetime "updated_at", null: false
  t.json "images"

4. Edit the model


mount_uploaders :images, ImageUploader

5. Edit controller

Add {images []} to the strong parameter so that it can be saved as an array in the column.


def book_params
  params.require(:book).permit(:title, :body, { images: [] })

6. Edit the view

** ① Create an image submission form **

By adding multiple: true, you can select multiple images.


= f.file_field :images, multiple: true

** ② Display the image **

Arrange the ʻimages column with" 5. Edit controller ", and since there are multiple images in it, turn it with ʻeach to take it out.

** * The image will not be displayed unless .to_s is added. ** **


  - book.images.each do |image|
    = image_tag image.to_s

About settings

1. Image size setting

ʻInclude CarrierWave :: MiniMagick` is added, and the size setting is described below it.

** ① process resize_to_fill ** (recommended) Crop from the specified position ('Center') at the specified size (100, 100) from the original image without maintaining the aspect ratio.


class ImageUploader < CarrierWave::Uploader::Base
  include CarrierWave::MiniMagick
  process resize_to_fill: [100, 100, 'Center']

スクリーンショット 2020-06-06 9.59.35.png

process resize_to_fit You can maintain the aspect ratio and resize the width up to 300px and the height up to 200px.


class ImageUploader < CarrierWave::Uploader::Base
  include CarrierWave::MiniMagick
  process resize_to_fit: [100, 100]

スクリーンショット 2020-06-06 10.00.23.png

2. Extension restrictions

Uncomment lines 38-40 of ʻimage_uploader.rb`. By default, you cannot upload if the extension is other than jpg, jpeg, gif, png.


class ImageUploader < CarrierWave::Uploader::Base
  def extension_whitelist
    %w(jpg jpeg gif png)

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