Ruby on rails 不允许的参数：<；型号名称>；嵌套表单属性（回形针）Rails 4

我搜索了所有类似的帖子，但无法找出我的代码有什么问题。
错误：不允许参数：照片。
我有一个用户模型，其中有许多项目，然后项目有许多照片。 下面是代码：
型号：

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结束

更改您的表格，我认为这将解决您的许多问题！成功了！：）

class Project < ActiveRecord::Base
belongs_to :user
has_many :photos, :dependent => :destroy 
accepts_nested_attributes_for :photos, :reject_if => lambda { |a| a[:photo].blank? }, :allow_destroy => true 
end


class Photo < ActiveRecord::Base

belongs_to :project
has_attached_file :photo, :styles => { :medium => "300x300>", :thumb => "100x100>" }, :default_url => "/images/:style/missing.png"
validates_attachment_content_type :photo, :content_type => /\Aimage\/.*\Z/
end

class ProjectsController < ApplicationController
before_filter :authenticate_user!
layout 'innerlayout'
before_action :find_user
def new
    @project = Project.new({:user_id => @user.id})
    @project.photos.build

end

def create
    @project = Project.new(project_params)
    if @project.save
        redirect_to(user_path(@user.id))
    else
        render(new_user_project_path(@user.id))
    end
end
...
def project_params
        params.require(:project).permit(:user_id,:title,:description, :photos_attributes => [:id, :photo])
    end

<%= form_for(:project, :url => user_projects_path(@user.id)) do |f| %>

    <%= render(:partial =>"project_form", :locals => {:f => f}) %>
<% end %>

    <%= f.hidden_field :user_id , :value=>@user.id %>

    <%= f.label :title, 'Title'%>
    <%= f.text_field :title%> 

    <%= f.label :description, 'Description' %>
    <%= f.text_field :description%>

    <%= f.fields_for :photos do |builder| %>
        <%= builder.label :photo, "Add Photo" %>
        <%= builder.file_field :photo %>
    <% end %>
    <%= submit_tag "Add", :class => "btn btn-primary" ,:value => nil %>

 create_table "photos", force: :cascade do |t|
t.integer  "project_id"
t.string   "photo_file_name"
t.string   "photo_content_type"
t.integer  "photo_file_size"
t.datetime "photo_updated_at"
t.datetime "created_at",         null: false
t.datetime "updated_at",         null: false