Cheat Sheet for Active Storage

active_storage_cheatsheet.rb

# SEE CONFIGURATION ON: https://github.com/rails/rails/blob/main/guides/source/configuring.md#configuring-active-storage

# Delete variations when config.active_storage.track_variants = true
my_model_instance.image.service.delete_prefixed(my_model_instance.image.key)

# List all variations on a model
# Here, `my_model_attachment_name` refers to the name I give to the attachment with the `:has_one_attached` macro.
# cf. https://edgeguides.rubyonrails.org/active_storage_overview.html
my_model_attachment_name = "image"
my_model_variations_transformations = MyModel.attachment_reflections[my_model_attachment_name].variants.keys.map do |variant_name|
   MyModel.first.public_send(my_model_attachment_name).variant(variant_name).variation.transformations
end
# Example of an output 
# =>
# [{:format=>"jpg", :resize_to_fit=>[400, 400], :saver=>{:quality=>30}},
#  {:format=>"jpg", :resize_to_fit=>[600, 600], :saver=>{:quality=>30}},
#  {:format=>"jpg", :resize_to_limit=>[800, 800], :saver=>{:quality=>70}}]

# List all existing variation digests
current_variant_variation_digests = my_model_variations_transformations.map do |transformations|
  # Use the same digest as ActiveRecord::Variation
  # cf. https://github.com/rails/rails/blob/main/activestorage/app/models/active_storage/variation.rb#L78
  OpenSSL::Digest::SHA1.base64digest Marshal.dump(transformations.symbolize_keys)
end

# Count unused old variants
all_variation_digests = ActiveStorage::VariantRecord.all.distinct.pluck(:variation_digest)
useless_digests = all_variation_digests - current_variant_variation_digests
unused_old_variants = ActiveStorage::VariantRecord.where(variation_digest: useless_digests)
unused_old_variants_count = unused_old_variants.count

# Delete unused variant records and their files from my storage
unused_old_variants.destroy_all

# Only delete files of unused blobs on your storage
useless_digests.each do |digest|
  ActiveStorage::Blob.service.delete(digest)
end

# Use cached public files with S3

# Add this to config/storage.yml
# public: true,
# upload: 
#   cache_control: public, max-age=<%= whatever I want %>, immutable

# If this is only for the variants, destroy all the variants and reupload them using variant.processed.url
# If this is for the original attachments and the variants, purge the attachments (cf. https://github.com/rails/rails/blob/3ea99f53fafbcacfda58b11e2c0537fc043742f2/activestorage/lib/active_storage/attached/one.rb#L7)

# RSpec config
config.before do
  ActiveStorage::Current.urls_options = {
    host: "example.com",
  }
end