将参数传递给上传器/从上传器内部访问模型的属性/让用户选择缩略图大小 [英] Passing a parameter to the uploader / accessing a model's attribute from within the uploader / letting the user pick the thumbnail size

问题描述

我想将图像裁剪为用户从列表中选择的大小（例如100x100px，200x200px等）
如何将属性传递给上载器或从内部获取模型的属性

I would like to crop an image to the size the user has selected from a list (e.g. 100x100px, 200x200px,...) How would I pass that attribute to the uploader or get the model's attribute from within the uploader?

无法通过以下方式从上传器内部访问模型的属性：

Accessing the model's attribute from within the uploader as following does not work:

version :thumb do
    thumbnail_size = model.thumbnail_size
    ...
    ...
end

我得到以下错误：

未定义的局部变量或方法`型号，用于＃

undefined local variable or method `model' for #

谢谢！
Florian

Thank you! Florian

推荐答案

为了能够访问模型的属性，我必须添加一个操纵助手。

In order to be able to access the model's attribute I had to add a manipulation helper.

class MyUploader < CarrierWave::Uploader::Base
  ...

  version :thumb do
    process :custom_thumbnail
    process :convert => 'jpg'
    ...
  end

  def custom_thumbnail
      width =  model.get_image_width     
      height = model.get_image_height

      manipulate! do |img|
        img.convert "#{width}x#{height}"
        img
      end
  end
end

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