需要帮助设置回形针

Question

我想第一次使用回形针。我尝试使用头像的用户，但是当我查看配置文件唯一显示的东西是'失踪'这个词。

class UsersController < ApplicationController 
    # GET /users 
    # GET /users.xml 
    def index 
     @users = User.all 

     respond_to do |format| 
      format.html # index.html.erb 
      format.xml { render :xml => @users } 
     end 
    end 

    # GET /users/1 
    # GET /users/1.xml 
    def show 
     @user = User.find(params[:id]) 

     respond_to do |format| 
      format.html # show.html.erb 
      format.xml { render :xml => @user } 
     end 
    end 

    # GET /users/new 
    # GET /users/new.xml 
    def new 
     @user = User.new 

     respond_to do |format| 
      format.html # new.html.erb 
      format.xml { render :xml => @user } 
     end 
    end 

    # GET /users/1/edit 
    def edit 
     @user = User.find(params[:id]) 
    end 

    # POST /users 
    # POST /users.xml 
    def create 
     @user = User.new(params[:user]) 

     respond_to do |format| 
      if @user.save 
       format.html { redirect_to(:users, :notice => 'Registration successfull.') } 
       format.xml { render :xml => @user, :status => :created, :location => @user } 
      else 
       format.html { render :action => "new" } 
       format.xml { render :xml => @user.errors, :status => :unprocessable_entity } 
      end 
     end 
    end 

    # PUT /users/1 
    # PUT /users/1.xml 
    def update 
     @user = User.find(params[:id]) 

     respond_to do |format| 
      if @user.update_attributes(params[:user]) 
       format.html { redirect_to(@user, :notice => 'User was successfully updated.') } 
       format.xml { head :ok } 
      else 
       format.html { render :action => "edit" } 
       format.xml { render :xml => @user.errors, :status => :unprocessable_entity } 
      end 
     end 
    end 

    # DELETE /users/1 
    # DELETE /users/1.xml 
    def destroy 
     @user = User.find(params[:id]) 
     @user.destroy 

     respond_to do |format| 
      format.html { redirect_to(users_url) } 
      format.xml { head :ok } 
     end 
    end 
end 

用户模式

class User < ActiveRecord::Base 
    acts_as_authentic 

    has_attached_file :avatar, :styles => { :medium => "300x300>", :thumb => "100x100>" } 

    validates_attachment_presence :avatar 
    validates_attachment_size :avatar, :less_than => 5.megabytes 
    validates_attachment_content_type :avatar, :content_type => ['image/jpeg', 'image/png'] 
end 

一旦我包括验证尝试创建或编辑用户

Avatar file name must be set. 

Answer 1

在视图中的表单定义，当我得到的错误，你有：multipart => true？沿线的东西：

<%= form_tag({:action => :upload}, :multipart => true) do %>