ruby-on-rails - 检测文件类型并调整图像大小

Question

我有支持 pdf 和图像的模型附件。如何检测它的图像，然后才调整它的大小？当它是回形针时，一切都很简单。但现在 ？ ;)

class Attachment < ActiveRecord::Base

        has_attached_file :attachment,
                styles:          lambda { |a| a.instance.is_image? ? {:small => "x200>", :medium => "x300>", :large => "x400>"}  : {:thumb => { :geometry => "100x100#", :format => 'jpg'}, :medium => { :geometry => "300x300#", :format => 'jpg'}}},

        def is_image?
                attachment.instance.attachment_content_type =~ %r(image)
        end

end

如何使用事件存储制作类似上面的内容？我这样尝试:

class Attachment < ApplicationRecord
  has_one_attached :file
  validates :file, presence: true

def file_url
if ???? (is image?)
rails_blob_url(file.variant(resize: '1920x1920').processed)
else
rails_blob_url(file)
  end
end

Answer 1

ActiveStorage 内置了流行内容类型的帮助程序，例如:图像、视频、音频等。图像是 image?:

if file.image?
  rails_representation_url(file.variant(resize: '1920x1920').processed)
else
  rails_blob_url(file)
end

API 文档:https://api.rubyonrails.org/classes/ActiveStorage/Blob.html#method-i-image-3F

音频？图片？文本？视频？