ruby-on-rails - 回形针图像尺寸自定义验证器

Question

这是我的 Image 模型，我在其中实现了一种验证附件尺寸的方法:

class Image < ActiveRecord::Base
  attr_accessible :file

  belongs_to :imageable, polymorphic: true

  has_attached_file :file,
                     styles: { thumb: '220x175#', thumb_big: '460x311#' }

  validates_attachment :file,
                        presence: true,
                        size: { in: 0..600.kilobytes },
                        content_type: { content_type: 'image/jpeg' }

  validate :file_dimensions

  private

  def file_dimensions(width = 680, height = 540)
    dimensions = Paperclip::Geometry.from_file(file.queued_for_write[:original].path)
    unless dimensions.width == width && dimensions.height == height
      errors.add :file, "Width must be #{width}px and height must be #{height}px"
    end
  end
end

这工作正常，但它不可重用，因为该方法采用固定的宽度和高度值。我想将其转换为自定义验证器，以便我也可以在其他模型中使用它。我已经阅读了有关此的指南，我知道它在 app/models/dimensions_validator.rb 中会是这样的:

class DimensionsValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    dimensions = Paperclip::Geometry.from_file(record.queued_for_write[:original].path)

    unless dimensions.width == 680 && dimensions.height == 540
      record.errors[attribute] << "Width must be #{width}px and height must be #{height}px"
    end
  end
end

但我知道我错过了一些东西，因为这段代码不起作用。问题是我想在我的模型中像这样调用验证:
validates :attachment, dimensions: { width: 300, height: 200} .

关于应该如何实现这个验证器的任何想法？

Answer 1

把它放在 app/validators/dimensions_validator.rb 中:

class DimensionsValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    # I'm not sure about this:
    dimensions = Paperclip::Geometry.from_file(value.queued_for_write[:original].path)
    # But this is what you need to know:
    width = options[:width]
    height = options[:height] 

    record.errors[attribute] << "Width must be #{width}px" unless dimensions.width == width
    record.errors[attribute] << "Height must be #{height}px" unless dimensions.height == height
  end
end

然后，在模型中:

validates :file, :dimensions => { :width => 300, :height => 300 }