在 Active storage Rails 5.2 中按文件名排序多个图像

Question

I have has_many_attached images relationship in Post model. I want to order the images by their filename when showing them on the Post show page. How can I order by filename?

Example:

<% @post.images.order("id DESC").each do |image| %>

Is it possible to just order by filename through something like active_storage_blob.filename or something?

Answer 1

When you add the has_many_attached macro to a class it actually adds the following relationships to your class

  class Post < ApplicationRecord
     has_many :image_attachments, -> { where(name: 'image') }, class_name: "ActiveStorage::Attachment", as: :record, inverse_of: :record, dependent: false
     has_many :image_blobs, through: :image_attachments, class_name: "ActiveStorage::Blob", source: :blob
  end

This means we can leverage the relationship to handle sorting by filename which is actually an attribute of the ActiveStorage::Blob rather than the attachment. To do this we reference to the relation defined in by the macro images in your case and then join to its natural relationship to the ActiveStorage::Blob so that we can sort based on these fields.

The final result would be

   <% @post.images.joins(:blobs).order('active_storage_blobs.filename ASC').each do |image| %>

Now all of the images will be sorted by the filename however since joins does not actually load any data and I am assuming you are referencing the the file name in your view we could also use

   <% @post.images.includes(:blobs).references(:blobs).order('active_storage_blobs.filename ASC').each do |image| %>

To have a single query that loads the images and the ActiveStorage::Blob data all at once to avoid the n + 1 issues that could arise from the original version.

Answer 2

For Rails 6 I needed

@post.images.includes(:blob).references(:blob).order('active_storage_blobs.filename ASC').each do |image|
  # ...
end

Answer 3

If you have the class setup with ActiveStorage like:

class Post < ApplicationRecord
  has_many_attached :images
end

You can run this to order and avoid N+1 queries

@post.images.includes(:blob).references(:blob).order(:filename)

Answer 4

If anyone is googling for general<\/strong> solution how to reorder has_many_attached<\/code> attachments you can do it by adding a Array\/JSON-Array\/Serialized field to the model which declares the has_many_attached<\/code> and store ids of ActiveStorage::Attachment in order. Then you can do something like:

# app/models/entry.rb
class Entry < ApplicationRecord
  has_many_attached :pictures


  def ordered_pictures
    pictures.sort_by{ |pic| ordered_picture_ids.index(pic.id) || (pic.id*100) }
  end

  def ordered_picture_ids=(ids)
    super(ids.map(&:to_i)) # convert any ids passed to this method to integer
                           # this is just for security reasons,
                           # you don't need to do this for the feature to work
  end
end