有条件地将样式应用于Rails 3.1中的回形针附件 [英] Conditionally applying styles to paperclip attachments in Rails 3.1

问题描述

我有以下型号：

Post.rb

  class Post< ActiveRecord :: Base 
 
 belongs_to：category 
 has_many：attachments，：dependent => ：销毁
 has_many：引用，：依赖=> ：销毁
 
 validates：title，：category_id，：content，：presence => true 
 
 acts_as_taggable_on：keywords 
 accept_nested_attributes_for：attachments，：allow_destroy => true，
：reject_if => proc {|属性|属性['photo']。blank？} 
 accept_nested_attributes_for：citations，：allow_destroy => true 
 
 end 
  

Attachment.rb

  class附件< ActiveRecord :: Base 
 
 belongs_to：post 
 
 has_attached_file：photo，：styles => {：medium => 637x471>，
：thumb => Proc.new {| instance | instance.resize}，
：carousel => Proc.new {| instance | instance.decide_style} 
}，
：url => /pictures/:style/:basename.:extension，
：path =>：rails_root / public / pictures /：style /：basename。：extension
 
 
 validates_attachment_content_type：photo，：content_type => ['image / png'，'image / jpg'，'image / jpeg'] 
 validates_attachment_size：photo，：less_than => 2.megabytes 
 
 
 ### End Paperclip #### 
 def decide_style 
 
＃catid = Post.find（param [：post_category_id] ）
＃在这里可以从表单中选择。 
 
 if（catid == 2）
＃400x800>或自定义样式
结束
 $ b $结束
 
 
 def resize 
 geo = Paperclip :: Geometry.from_file（photo.to_file（：原始））
 
 ratio = geo.width / geo.height 
 
 min_width = 142 
 min_height = 119 
 
如果比例> 1 
＃水平图像
 final_height = min_height 
 final_width = final_height *比例
＃{final_width.round} x＃{final_height.round}！ 
 else 
＃垂直图片
 final_width = min_width 
 final_height = final_width *比例
＃{final_height.round} x＃{final_width.round}！ 
 end 
 end 
 
 end 
  

我是试图有条件地应用样式，基于从表单上的下拉菜单中选择。

想法？

p> Rishi

解决方案

看起来你正在尝试将它基于 category_id 值在 Post 模型上，对吗？如果是这样，您实际上可以在附件选项中传递一个lambda作为：styles 条目的值，其中包括附件作为属性。

  has_attached_file：photo，
：styles => lambda {| attachment | {
：medium => 637x471>，
：thumb => attachment.instance.resize，
：carousel => attachment.instance.decide_style，
}}，
：url => /pictures/:style/:basename.:extension，
：path =>：rails_root / public / pictures /：style /：basename。：extension
  

附件是 Paperclip :: Attachment 对象，然后调用实例方法返回你的模型实例。

然后在你的 decide_style 方法，您可以根据需要将它基于模型的 category_id 值。

  def decision_style 
 case category_id 
 when 1 then200x400> 
当2然后400x800> 
 else50x50＃
 end 
 end 
  

I have the following models:

Post.rb

  class Post < ActiveRecord::Base

  belongs_to :category
  has_many :attachments, :dependent => :destroy
  has_many :citations, :dependent => :destroy

  validates :title, :category_id, :content, :presence =>true

  acts_as_taggable_on :keywords
  accepts_nested_attributes_for :attachments, :allow_destroy => true, 
         :reject_if => proc { |attributes| attributes['photo'].blank?}
  accepts_nested_attributes_for :citations, :allow_destroy=>true

end

Attachment.rb

  class Attachment < ActiveRecord::Base

  belongs_to :post

  has_attached_file :photo, :styles => { :medium => "637x471>", 
                :thumb => Proc.new { |instance| instance.resize },
                :carousel => Proc.new { |instance| instance.decide_style }
                },
                :url => "/pictures/:style/:basename.:extension",
                :path =>":rails_root/public/pictures/:style/:basename.:extension"


  validates_attachment_content_type :photo, :content_type => ['image/png', 'image/jpg', 'image/jpeg']                  
    validates_attachment_size :photo, :less_than => 2.megabytes         


   ### End Paperclip ####
  def decide_style

   # catid = Post.find(param[:post_category_id])
   # something here to get the selection from the form.

      if(catid == 2)
      # "400x800>" or custom style here
      end

      end


 def resize     
 geo = Paperclip::Geometry.from_file(photo.to_file(:original))

 ratio = geo.width/geo.height  

 min_width  = 142
 min_height = 119

 if ratio > 1
   # Horizontal Image
   final_height = min_height
   final_width  = final_height * ratio
   "#{final_width.round}x#{final_height.round}!"
 else
   # Vertical Image
   final_width  = min_width
   final_height = final_width * ratio
   "#{final_height.round}x#{final_width.round}!"
  end
 end 

 end

I am trying to conditionally apply a style, based on the selection made from a drop down on the form. I am just not sure as to where the decision as to what style should be chosen is implemented.

Thoughts?

Rishi

解决方案

It looks like you're trying to base it upon the category_id value on the Post model, is that right? If so, you can actually pass a lambda as the value of the :styles entry in your attachment options, which includes the attachment as an attribute.

has_attached_file :photo,
    :styles => lambda { |attachment| {
      :medium => "637x471>", 
      :thumb => attachment.instance.resize,
      :carousel => attachment.instance.decide_style,
    } },
    :url => "/pictures/:style/:basename.:extension",
    :path =>":rails_root/public/pictures/:style/:basename.:extension"

The attachment is a Paperclip::Attachment object, and calling the instance method on it returns your model instance.

Then in your decide_style method, you can base it upon your model's category_id value as needed.

def decide_style
  case category_id
  when 1 then "200x400>"
  when 2 then "400x800>"
  else "50x50#"
  end
end

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