如何将 Carrierwave 文件迁移到 Rails 中另一个模型的列答案

【问题标题】：How to migrate a Carrierwave file to a column in another model in Rails如何将 Carrierwave 文件迁移到 Rails 中另一个模型的列
【发布时间】：2019-02-07 21:11:46
【问题描述】：

我有一个使用 Carrierwave 存储文件的现有模型。我想将该文件移至新模型，但我似乎无法正确读取该文件

这是我现有的模型：

class ShipmentNote < ActiveRecord::Base
  has_many :shipment_note_files # this is actually the new model I want to move the files to
  mount_uploader :file, DocumentUploader
  ....
end

还有我的新模型：

class ShipmentNoteFile < ActiveRecord::Base
  belongs_to :shipment_note
  mount_uploader :file, DocumentUploader
end

这是我认为可行的：

ShipmentNote.where.not(file: nil).each do |shipment_note|
  # create a new file in the shipment_note_files
  shipment_note.shipment_note_files.create(file: shipment_note.file)
  # remove from shipment_note
  shipment_note.remove_file!
  shipment_note.save
end

但它抛出以下错误，暗示文件字段为空：

PG::NotNullViolation: ERROR:  null value in column "file" violates not-null constraint
DETAIL:  Failing row contains (15, null, 46689, 2019-02-07 20:56:54.503714, 2019-02-07 20:56:54.503714, null).
: INSERT INTO "shipment_note_files" ("file", "shipment_note_id", "created_at", "updated_at") VALUES ($1, $2, $3, $4) RETURNING "id"

【问题讨论】：

标签： ruby-on-rails-4 carrierwave data-migration

【解决方案1】：

问题是该文件在 S3 上确实不存在。我不得不挽救错误并且一切正常：

ShipmentNote.where.not(file: nil).each do |shipment_note|
  begin
    # create a new file in the shipment_note_files
    shipment_note.shipment_note_files.create(file: shipment_note.file)
    # remove from shipment_note
    shipment_note.remove_file!
    shipment_note.save
  rescue => exception
    p "file not exist: #{shipment_note.id}"
  end
end

【讨论】：