class ActiveStorage::Attached::Changes::CreateMany

def assign_associated_attachments
  record.public_send("#{name}_attachments=", persisted_or_new_attachments)
end

def attachments
  @attachments ||= subchanges.collect(&:attachment)
end

def blobs
  @blobs ||= subchanges.collect(&:blob)
end

def build_subchange_from(attachable)
  ActiveStorage::Attached::Changes::CreateOneOfMany.new(name, record, attachable)
end

def initialize(name, record, attachables, pending_uploads: [])
  @name, @record, @attachables = name, record, Array(attachables)
  blobs.each(&:identify_without_saving)
  @pending_uploads = Array(pending_uploads) + subchanges_without_blobs
  attachments
end

def persisted_or_new_attachments
  attachments.select { |attachment| attachment.persisted? || attachment.new_record? }
end

def reset_associated_blobs
  record.public_send("#{name}_blobs").reset
end

def save
  assign_associated_attachments
  reset_associated_blobs
end

def subchanges
  @subchanges ||= attachables.collect { |attachable| build_subchange_from(attachable) }
end

def subchanges_without_blobs
  subchanges.reject { |subchange| subchange.attachable.is_a?(ActiveStorage::Blob) }
end

def upload
  pending_uploads.each(&:upload)
end