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我有大麻烦...

我已经通过我的 Rails 应用程序将大约 500 张图片上传到了 S3，有几种不同的尺寸。现在我意识到我需要将这些图像尺寸存储到我的数据库中。我这样做的方法是使用此迁移：

class AddImageDimensionsToImages < ActiveRecord::Migration
  def change

    # add image columns
    add_column :images, :small_width, :integer
    add_column :images, :small_height, :integer
    add_column :images, :medium_width, :integer
    add_column :images, :medium_height, :integer
    add_column :images, :large_width, :integer
    add_column :images, :large_height, :integer
    add_column :images, :original_width, :integer
    add_column :images, :original_height, :integer

    # loop all images
    Image.all.each do |image|

      # get sizes
      geo_small = Paperclip::Geometry.from_file(image.image.to_file(:small))
      geo_medium = Paperclip::Geometry.from_file(image.image.to_file(:medium))
      geo_large = Paperclip::Geometry.from_file(image.image.to_file(:large))
      geo_original = Paperclip::Geometry.from_file(image.image.to_file(:original))

      # set sizes
      image.small_width = geo_small.width if geo_small
      image.small_height = geo_small.height if geo_small

      image.medium_width = geo_medium.width if geo_medium
      image.medium_height = geo_medium.height if geo_medium

      image.large_width = geo_large.width if geo_large
      image.large_height = geo_large.height if geo_large

      image.original_width = geo_original.width if geo_original
      image.original_height = geo_original.height if geo_original

      # save image
      image.save

    end

  end

end

当我运行此迁移时，它是这样的：

...

-- add_column(:images, :small_width, :integer)
   -> 2.0866s
-- add_column(:images, :small_height, :integer)
   -> 0.0092s
-- add_column(:images, :medium_width, :integer)
   -> 0.0073s

...

Command :: identify -format %wx%h '/app/tmp/HayUnFinal_1620120408-4-qpzyym.jpg[0]'
[AWS S3 200 0.106467] get_object(:bucket_name=>"aa",:key=>"original/34/HayUnFinal_16.jpg")

Command :: identify -format %wx%h '/app/tmp/HayUnFinal_1620120408-4-1vqo71y.jpg[0]'
[paperclip] Saving attachments.
[AWS S3 200 0.152898] get_object(:bucket_name=>"aa",:key=>"small/64/Portrait_2.jpg")

Command :: identify -format %wx%h '/app/tmp/Portrait_220120408-4-i1ohlr.jpg[0]'
[AWS S3 200 0.055378] get_object(:bucket_name=>"aa",:key=>"medium/64/Portrait_2.jpg")

Command :: identify -format %wx%h '/app/tmp/Portrait_220120408-4-viizzf.jpg[0]'
[AWS S3 200 0.079235] get_object(:bucket_name=>"aa",:key=>"large/64/Portrait_2.jpg")

Command :: identify -format %wx%h '/app/tmp/Portrait_220120408-4-1d2u00o.jpg[0]'
[AWS S3 200 0.066724] get_object(:bucket_name=>"aa",:key=>"original/64/Portrait_2.jpg")

Command :: identify -format %wx%h '/app/tmp/Portrait_220120408-4-jq9wmg.jpg[0]'
[paperclip] Saving attachments.
[AWS S3 200 0.104891] get_object(:bucket_name=>"aa",:key=>"small/58/Bansah_24.jpg")

Command :: identify -format %wx%h '/app/tmp/Bansah_2420120408-4-an2mpt.jpg[0]'
[AWS S3 200 0.064148] get_object(:bucket_name=>"aa",:key=>"medium/58/Bansah_24.jpg")

Command :: identify -format %wx%h '/app/tmp/Bansah_2420120408-4-tzmnup.jpg[0]'
[AWS S3 200 0.051090] get_object(:bucket_name=>"aa",:key=>"large/58/Bansah_24.jpg")

Command :: identify -format %wx%h '/app/tmp/Bansah_2420120408-4-1pa0rxh.jpg[0]'
[AWS S3 200 0.063531] get_object(:bucket_name=>"aa",:key=>"original/58/Bansah_24.jpg")

Command :: identify -format %wx%h '/app/tmp/Bansah_2420120408-4-kogk2g.jpg[0]'
[paperclip] Saving attachments.

rake aborted!
An error has occurred, this and all later migrations canceled:

can't convert nil into String

耙中止！它似乎适用于几个图像，但随后迁移失败。我真的不知道那个 nil 来自哪里，以及如何防止它。谁能帮我这个？

额外问题：这是处理保存已上传图像的图像尺寸任务的一种方法吗？

提前非常感谢！

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1 回答 1

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数据库中的某些图像行具有空图像值。像这样的检查成功了：

Image.all.each do |image|

  # check that we have an image
  if image.image_file_size

    ...

  end

end
于 2012-04-15T19:46:55.070 回答