为什么我会在讨论中遇到“NameError”？

Question

我目前正在研究Ruby on Rails应用程序，该应用程序涉及用户使用微博创建讨论和评论。这是一个非常简单的概念，但我是新的，并遇到了一些麻烦。

当试图看看讨论页面（讨论指数）我得到的错误“在讨论＃指数NameError”：

undefined local variable or method `discussion' for #<#<Class:0x00000100c6e020>:0x0000010380edd8> 

这是我的讨论控制器：

class DiscussionsController < ApplicationController 
    before_filter :signed_in_user, only: [:index, :edit, :update] 


    def show 
    @user = User.find(params[:id]) 
    @discussions = @user.discussion.paginate(page: params[:page]) 
    @microposts = @user.micropost.paginate(page: params[:page]) 
    end 

    def index 
    @discussions = Discussion.all 
    end 

    def create 
    @discussion = current_user.discussions.build(params[:discussion]) 
    if @discussion.save 
     flash[:success] = "Discussion Started!" 
     redirect_to root_url 
    else 
     render 'static_pages/home' 
    end 
    end 

    def destroy 
    end 

    def edit 
    end 

    def update 
    end 

    def new 
    end 
end 

这是我的Micropost形式：

<% @micropost = Micropost.new %> 
<% @micropost.discussion_id = discussion.id %> 

<%= form_for(@micropost) do |f| %> 
    <%= render 'shared/error_messages', object: f.object %> 
    <div class="field"> 
     <%= f.text_area :content, placeholder: "Compose new micropost..." %> 
    </div> 
    <%= f.hidden_field :discussion_id, discussion.id%> 

    <%= f.submit "Post", class: "btn btn-large btn-primary" %> 
<% end %> 

这是我的讨论部分：

<% content_for :script do %> 
    <%= javascript_include_tag 'hover_content' %> 
<% end %> 

<li> 
    <div class = "intro-bar"><span class = "intro"><%=discussion.intro %></span></div> 
    <div class = "content-bar"> 
    <span class = "content"><%= discussion.content %></span> 
    <div class = "buttons"> 
     <div class = "vote-neg"><%= link_to "Break Up", signup_path,class: "btn btn-large btn-breakup" %></div> 
     <div class = "vote-plus"><%= link_to "Stay Together", signup_path,class: "btn btn-large btn-staytogether" %></div> 
    </div> 
    </div> 
</li> 

<span class = "timestamp"> 
    Posted <%= time_ago_in_words(discussion.created_at) %> ago. 
    </span> 

<div class = "comments"> 
    <% discussion.microposts.each do |micropost| %> 
     <li> 
     <div class = "post-comment"><%= micropost.content%></div> 
     </li> 
    <% end %> 
</div> 

<% if signed_in? %> 
    <div class = "row"> 
     <aside class = "span4"> 
     <section> 
      <%= render 'shared/micropost_form', :locals => {:discussion => discussion }%> 
     </section> 
     </aside> 
    </div> 
<% end %> 

这是我的微柱控制器：

class MicropostsController < ApplicationController 
    before_filter :signed_in_user, only: [:create, :destroy] 

    def index 
    end 

    def create 
    @discussion = current_user.discussions.new 
    @micropost = current_user.microposts.build(params[:micropost]) 
    if @micropost.save 
     flash[:success] = "Posted!" 
     redirect_to root_url 
    else 
     render 'static_pages/home' 
    end 
    end 

    def destroy 
    end 
end 

这是我的讨论模式：

class Discussion < ActiveRecord::Base 
    attr_accessible :content, :intro 
    has_many :microposts, dependent: :destroy 

    belongs_to :user 

    validates :content, presence: true, length: { maximum: 600 } 
    validates :intro, presence: true 

    default_scope order: 'discussions.created_at DESC' 
end 

这是我的用户模型：

class User < ActiveRecord::Base 
    attr_accessible :email, :username, :age, :sex, :points, :password, :password_confirmation 
    has_secure_password 
    has_many :microposts, dependent: :destroy 
    has_many :discussions, dependent: :destroy 


    before_save {|user| user.email = email.downcase} 
    before_save :create_remember_token 

    validates :username, presence: true, length: {maximum: 15} 
    VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i 
    validates :email, presence: true, format: { with: VALID_EMAIL_REGEX }, uniqueness: {case_sensitive: false} 
    validates :age, presence: true 
    validates :sex, presence: true 
    validates :password, presence: true, length: { minimum: 6 } 
    validates :password_confirmation, presence: true 

    private 

    def create_remember_token 
    self.remember_token = SecureRandom.urlsafe_base64 
    end 

end 

这是我的讨论索引：

<% provide(:title, "Discussions") %> 
<h1>Discussions</h1> 
<ul class = "discussions"> 
    <% @discussions.each do |discussion| %> 
     <li> 
     <%= render :partial =>"discussions/discussion", :locals=>{:discussion=>discussion} %> 
     </li> 
    <% end %> 
</ul> 

Answer 1

尝试改写这行：

<%= render 'shared/micropost_form', :locals => {:discussion => discussion }%> 

为：

<%= render 'shared/micropost_form', :discussion => discussion %>