NoMethodError Rails的多文件上傳

Question

我就越來越多文件上傳在我的應用程序的模型工作的工作，我已經包含下面的代碼：

delivers_controller.rb

# POST /delivers 

def create 
    @deliver = Deliver.new(params[:deliver]) 

    process_file_uploads(@deliver) 

    if @deliver.save 
    flash[:notice] = 'Task was successfully created.' 
    redirect_to(@deliver) 
    else 
    render :action => "new" 
    end 
end 

protected 

def process_file_uploads(deliver) 
    i = 0 
    while params[:attachment]['file_'+i.to_s] != "" && !params[:attachment]['file_'+i.to_s].nil? 
     deliver.assets.build(:data => params[:attachment]['file_'+i.to_s]) 
     i += 1 
    end 
end 

交付。 RB

has_many :assets, :as => :attachable, :dependent => :destroy 

    validate :validate_attachments 

    Max_Attachments = 5 
    Max_Attachment_Size = 5.megabyte 

    def validate_attachments 
     errors.add_to_base("Too many attachments - maximum is #{Max_Attachments}") if assets.length > Max_Attachments 
     assets.each {|a| errors.add_to_base("#{a.name} is over #{Max_Attachment_Size/1.megabyte}MB") if a.file_size > Max_Attachment_Size} 
    end 

assets_controller.rb

class AssetsController < ApplicationController 

    def show 
    asset = Asset.find(params[:id]) 
    # do security check here 
    send_file asset.data.path, :type => asset.data_content_type 
    end 

    def destroy 
     asset = Asset.find(params[:id]) 
     @asset_id = asset.id.to_s 
     @allowed = Deliver::Max_Attachments - asset.attachable.assets.count 
     asset.destroy 
    end 

end 

asset.rb

class Asset < ActiveRecord::Base 
    has_attached_file :data, 

    belongs_to :attachable, :polymorphic => true 

    def url(*args) 
    data.url(*args) 
    end 

    def name 
    data_file_name 
    end 

    def content_type 
    data_content_type 
    end 

    def file_size 
    data_file_size 
    end 
end 

每當我創建一個新的交付項目，並嘗試將出現以下錯誤的任何文件：

NoMethodError in DeliversController#create 

You have a nil object when you didn't expect it! 
You might have expected an instance of ActiveRecord::Base. 
The error occurred while evaluating nil.[] 
/Users/danny/Dropbox/SVN/railsapps/macandco/surveymanager/trunk/app/controllers/delivers_controller.rb:60:in `process_file_uploads' 
/Users/danny/Dropbox/SVN/railsapps/macandco/surveymanager/trunk/app/controllers/delivers_controller.rb:46:in `create' 

new.html .erb（交付視圖）

<% content_for :header do -%> 
    Deliver Repositories 
<% end -%> 

<% form_for(@deliver, :html => { :multipart => true }) do |f| %> 
    <%= f.error_messages %> 
    <p> 
    <%= f.label :caseref %><br /> 
    <%= f.text_field :caseref %> 
    </p> 
    <p> 
    <%= f.label :casesubject %><br /> 
    <%= f.text_area :casesubject %> 
    </p> 


    <p> 
    <%= f.label :description %><br /> 
    <%= f.text_area :description %> 
    </p> 

    <p>Pending Attachments: (Max of <%= Deliver::Max_Attachments %> each under <%= Deliver::Max_Attachment_Size/1.megabyte%>MB) 
     <% if @deliver.assets.count >= Deliver::Max_Attachments %> 
     <input id="newfile_data" type="file" disabled /> 
     <% else %> 
     <input id="newfile_data" type="file" /> 
     <% end %> 
     <div id="attachment_list"><ul id="pending_files"></ul></div> 

    </p> 
    <p> 
    <%= f.submit 'Create' %> 
    </p> 
<% end %> 

<%= link_to 'Back', delivers_path %> 

Show.html.erb（推出視圖）

<% content_for :header do -%> 
    Deliver Repositories 
<% end -%> 

<p> 
    <b>Title:</b> 
    <%=h @deliver.caseref %> 
</p> 
<p> 
    <b>Body:</b> 
    <%=h @deliver.casesubject %> 
</p> 

<p><b>Attached Files:</b><div id="attachment_list"><%= render :partial => "attachment", :collection => @deliver.assets %></div></p> 

<%= link_to 'Edit', edit_deliver_path(@deliver) %> | <%= link_to 'Back', deliver_path %> 

<%- if logged_in? %> 
<%= link_to 'Edit', edit_deliver_path(@deliver) %> | 
<%= link_to 'Back', delivers_path %> 
<% end %> 

_attachment.html.erb（推出視圖）

<% if !attachment.id.nil? %><li id='attachment_<%=attachment.id %>'><a href='<%=attachment.url %>'><%=attachment.name %></a> (<%=attachment.file_size/1.kilobyte %>KB) 
<%= link_to_remote "Remove", :url => asset_path(:id => attachment), :method => :delete, :html => { :title => "Remove this attachment", :id => "remove" } %></li> 
<% end %> 

我一直在敲打我的頭靠在牆上一整天都有錯誤，如果任何人都可以點亮它，我會永遠感激！

謝謝，

丹尼

Answer 1

該錯誤消息指示params[:attachment]是nil內部process_file_uploads()，這會導致params[:attachment]['file_'+i.to_s]引發異常。

發生這種情況是因爲new.html.erb中沒有名爲attachment的字段。