Question

当我为：photo字段选择新值并更新时，我的更新表单给了我这个错误。当更新和保存用户名，手机或电子邮件等非图像字段时，它不会出错。我正在使用paperclip作为文件附件管理宝石。

end

attr_accessible :photo # this is where the error points to
has_attached_file :photo,
:styles => {
  :thumb=> "100x100#",

这里是完整的跟踪：http://pastie.org/private/etie0qfqujkvrzpetpuqw

这是edit.html.erb：

<h1>Add A teacher</h1>

<%= form_for @teacher, :url => { :action => 'update', :id => @teacher.id}, :html => { :multipart => true } do |f| %>
<table summary="teacher form fields">
   <tr>
     <th>First Name*</th>
     <td><%= f.text_field :firstname %></td>
   </tr>
   <tr>
     <th>Last Name*</th>
     <td><%= f.text_field :lastname %></td>
   </tr>
   <tr>
     <th>Email*</th>
     <td><%= f.email_field :email %></td>
   </tr>
   <tr>
     <th>Cellphone</th>
     <td><%= f.telephone_field :cellphone %></td>
   </tr>
   <tr>
     <th>Username*</th>
     <td><%= f.text_field :username %></td>
   </tr>
   <tr>
   <tr>
     <th>Password*</th>
     <td><%= f.password_field :password %></td>
   </tr>
   <tr>
     <th>Confirm Password*</th>
     <td><%= f.password_field :password_confirmation %></td>
   </tr>
   <tr>
     <th>Address Street#</th>
     <td><%= f.text_field :addr_streetno %></td>
     <th>Apt #</th>
     <td><%= f.number_field :addr_aptno %></td>
   </tr>
   <tr>
     <th>City</th>
     <td><%= f.text_field :addr_city %></td>
     <th>State</th>
     <td><%= f.text_field :addr_state %></td>
     <th>Zip</th>
     <td><%= f.number_field :addr_zip %></td>
   </tr>
   <tr>
     <th>Photo</th>
     <td><%= f.file_field :photo %></td>
   </tr>
</table>

   <%= f.submit 'Update teacher' %>
<% end %>

<% if @teacher.errors.any? %>
    <ul class="Signup_Errors">
    <% for message_error in @teacher.errors.full_messages %>
      <li>* <%= message_error %></li>
    <% end %>
    </ul>
  <% end %>
</div>

这是控制器：

class TeacherController < ApplicationController
  def index
      @teachers= Teacher.all 
  end

  def new
      @teacher = Teacher.new
  end

  def create
      @teacher = Teacher.new(teacher_params)
      if @teacher.save
        flash[:notice] = "Teacher created."
        redirect_to :action => 'index'
      else
        render :action => 'new'
      end
  end

  def edit
    @teacher = Teacher.find(params[:id])
  end

  def update
     @teacher = Teacher.find(params[:id])
     # Update the object
     if @teacher.update_attributes(teacher_params)
       # If update succeeds, redirect to the list action
       flash[:notice] = "Teacher updated."
       redirect_to :action => 'show', :id => @teacher.id
     else
       # If update fails, redisplay the form so user can fix problems
       render :action => 'edit'
     end
  end

  def show
    @teacher = Teacher.find(params[:id])
  end

private

    def teacher_params
      params.require(:teacher).permit(:firstname, 
                                      :lastname,  
                                      :email, 
                                      :cellphone, 
                                      :username, 
                                      :password,
                                      :password_confirmation,
                                      :addr_streetno, 
                                      :addr_aptno, 
                                      :addr_city, 
                                      :addr_state,
                                      :addr_zip, 
                                      :photo)
    end
end

以下是模型：

class Teacher < ActiveRecord::Base

    has_many :students

    has_secure_password

    EMAIL_REGEX = /\A[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\z/i
    CELLPHONE_REGEX = /\A([0-9]( |-)?)?(\(?[0-9]{3}\)?|[0-9]{3})( |-)?([0-9]{3}( |-)?[0-9]{4}|[a-zA-Z0-9]{7})\z/i
    validates :firstname, :presence => true
    validates :lastname, :presence => true   
    validates :username, :presence => true, :uniqueness => true, :length => { :in => 3..20 }
    validates :email, :presence => true, :uniqueness => true, :format => EMAIL_REGEX
    validates :cellphone, :presence => true, :format => CELLPHONE_REGEX
    [:addr_aptno, :addr_zip].each do |n|
        validates n, numericality: { only_integer: true, 
                                    :greater_than => 0,
                                    :allow_blank => true
                                   }
    end
    attr_accessible :photo
    has_attached_file :photo,
     :styles => {
      :thumb=> "100x100#",
      :small  => "150x150>",
      :medium => "300x300>",
      :large =>   "400x400>" }
end

Answer 1

回答原始问题

更新图像字段会给出NoMethodError未定义的方法name' for nil:NilClass in update'

OP没有使用amy gem来帮助上传导致此问题的Rails应用程序中的文件。建议使用其中一个众所周知的宝石 Paperclip 或 CarrierWave 。

回答修改后的问题

使用回形针进行更新时，
未定义的方法`attr_accessible' 更新表格中的照片字段

当您使用Rails 4时，attr_accessible :photo将无效，因为它已被删除。相反，您需要在Strong Parameters方法中允许:photo属性，将teacher_params用于属性白名单。

因此，您只需从attr_accessible :photo模型中删除Teacher。

Answer 2

添加重新启动rails服务器（因为添加了回形针gem）＆amp;将add_attachment：，：添加到迁移文件并运行它，表中的以下字段（add_attachment：老师：照片用于在这里运行）

t.string   "photo_file_name"
t.string   "photo_content_type"
t.integer  "photo_file_size"
t.datetime "photo_updated_at"

此外，我不得不在控制器文件中的强参数分配调用中添加：photo，并且还必须在迁移文件＆amp;中添加add_attachment：teachers：photo。运行。有几件事。

未定义的方法`attr_accessible'，同时使用回形针以更新形式更新照片字段

2 个答案: