我正在尝试扩展 Rails 教程示例应用程序以包含回复。
我创建了一个 Recipient 模型，其中包含一个user_id用于指定回复的收件人和一个micropost_id.
我将以下内容添加到我的用户模型中。
class User < ActiveRecord::Base
...
has_many :replies, foreign_key: "user_id", class_name: "Recipient", dependent: :destroy
has_many :received_replies, through: :replies, source: :micropost
...
def feed
Micropost.from_followed_by_and_replying_to(self)
end
...
end
这对我的 Micropost 模型：
class Micropost < ActiveRecord::Base
belongs_to :user
...
has_many :recipients, dependent: :destroy
has_many :replied_users, through: :recipients, :source => "user"
...
def self.from_followed_by_and_replying_to(user)
followed_ids = "SELECT followed_id FROM relationships
WHERE followed_id = :user_id"
replier_ids = "SELECT micropost_id FROM recipients
WHERE user_id = :user_id"
where("user_id in (#{followed_ids})
OR id in (#{replier_ids}) OR user_id = :user_id",
user_id: user.id)
end
...
end
StaticPages#home 操作加载提要：
class StaticPagesController < ApplicationController
def home
if signed_in?
@micropost = current_user.microposts.build
@feed_items = current_user.feed.paginate(page: params[:page])
end
end
...
end
然后，当登录并访问主页时，我在这一行获得NoMethodError in StaticPages#Home了共享feed_item部分 (app/views/shared/_feed_item.html.erb)：
<%= link_to gravatar_for(feed_item.user), feed_item.user %>
它是undefined method 'email' for nil:NilClass（大概user.email是gravatar_for辅助方法使用的。
当我Micropost.from_followed_by_and_replying_to([some user])在 Rails 控制台中调用时，返回来自关注用户的微博和回复都没有问题，所以我认为我的数据库查询在这里不正确。任何帮助表示赞赏，我真的很难过。
编辑：（从这些中删除了一些 HTML）
应用程序/views/static_pages/home.html.erb：
<% if signed_in? %>
...
<%= render 'shared/user_info' %>
<%= render 'shared/stats' %>
<%= render 'shared/micropost_form' %>
<%= render 'shared/feed' %>
...
<% else %>
...
<% end %>
应用程序/视图/共享/_feed.html.erb：
<% if @feed_items.any? %>
<%= render partial: 'shared/feed_item', collection: @feed_items %>
<%= will_paginate @feed_items %>
<% end %>
app/views/shared/_feed_items.html.erb：
<li id="<%= feed_item.id %>">
<%= link_to gravatar_for(feed_item.user), feed_item.user %>
<%= link_to feed_item.user.name, feed_item.user %>
...
</li>