Rails 6最小文件上传

config.active_storage.service = :local

rails generate model Attachment

class CreateAttachments < ActiveRecord::Migration[6.0]
  def change
    create_table :attachments do |t|
      t.string :name
      t.text :description
      t.timestamps
    end
  end
end

rails db:migrate

class Attachment < ApplicationRecord
  has_one_attached :file
end

class AttachmentsController < ApplicationController
  def new
    @attachment = Attachment.new
  end

  def create
    @attachment = Attachment.new(attachment_params)
    if @attachment.save
      redirect_to @attachment, notice: 'Attachment was successfully created.'
    else
      render :new
    end
  end

  private

  def attachment_params
    params.require(:attachment).permit(:name, :description, :file)
  end
end

<%= form_with(model: @attachment, url: attachments_path, local: true) do |form| %>
  <%= form.label :name %>
  <%= form.text_field :name %>

  <%= form.label :description %>
  <%= form.text_area :description %>

  <%= form.label :file %>
  <%= form.file_field :file %>

  <%= form.submit %>
<% end %>

<% if @attachment.file.attached? %>
  <%= image_tag @attachment.file %>
<% end %>