Rails Read csv file data with active storage

Question

I have this class and I am using active storage

class MaterialsUpload < ApplicationRecord
  has_one_attached :csv_file
end

This is the attachment

#<ActiveStorage::Attached::One:0x007ff1f0be9e90
 @dependent=:purge_later,
 @name="csv_file",
 @record=
  #<MaterialsUpload:0x007ff1f0c604f0
   id: 3,
   success: 0,
   errors_list: [],
   total: 0,
   created_at: Mon, 12 Feb 2018 14:43:35 UTC +00:00,
   updated_at: Mon, 12 Feb 2018 14:43:35 UTC +00:00>>

Is there a way I can read the data so I can do something like this

string = materials_upload.csv_file.read
CSV.parse(csv_string, headers: true) do |row|
  # do something
end

Answer 1

Use #download to obtain the file’s contents:

CSV.parse(materials_upload.csv_file.download, headers: true) do |row|
  # ...
end

Downloads the file associated with this blob. If no block is given, the entire file is read into memory and returned. That’ll use a lot of RAM for very large files. If a block is given, then the download is streamed and yielded in chunks.