来自 Model 的动态样式大小的回形针附件 [英] Paperclip attachments with dynamic style sizes from Model

问题描述

使用 Rails 2，我尝试通过另一个模型与回形针模型分离不同的动态图像大小.我目前使用 Proc 的方法如下所示:

Using Rails 2, I try to separate different, dynamic image sizes trough another Model from the Paperclip-Model. My current approach, using a Proc, looks the following:

class File < ActiveRecord::Base
  has_many :sizes, :class_name => "FileSize"
  has_attached_file(
    :attachment,
    :styles => Proc.new { |instance| instance.attachment_sizes }
  )

  def attachment_sizes
    sizes = { :thumb => ["100x100"] }
    self.sizes.each do |size|
      sizes[:"#{size.id}"] = ["#{size.width}x#{size.height}"]
    end
    sizes
  end
end

class FileSize < ActiveRecord::Base
  belongs_to    :file

  after_create  :reprocess
  after_destroy :reprocess

  private

  def reprocess
    self.file.attachment.reprocess!
  end
end

似乎一切正常，但显然没有处理任何样式，也没有创建任何图像.

Everything seems to work out fine but apparently no styles are processed and no image is being created.

有人做过这样的事情吗?

Did anyone manage doing stuff like this?

-- 更新 --

显然，实例上的attachment_sizes 方法有时不是为# 定义的——但实例实际上不应该是#?对我来说，这看起来像是在改变实例..

Obviously the method attachment_sizes on instance sometimes is not defined for # - but shouldn't instance actually be #? For me this looks like altering instance..

推荐答案

解决方案很简单.instance 在我的第一个例子中，Proc 是 Paperclip::Attachment 的一个实例.由于我想调用 File 方法，因此必须在 Proc 中获取调用实例:

The solution is simple. instance in my first example Proc is an instance of Paperclip::Attachment. As I want to call a File method, one has to get the calling instance inside the Proc:

Proc.new { |clip| clip.instance.attachment_sizes }

instance 表示给定示例中的 File-instance.

instance represents File-instance in the given example.

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