我正在使用rails跟踪teamtreehouse.com上的Treebook教程（制作一个facebook克隆）。我创建了一个userfriendships控制器，并且在友谊视图的index.html页面中尝试引用朋友的全名时出现此错误：未定义的方法`full_name'为nil：NilClass 。问题出现在第4行（这是/views/user_friendships/index.html）
<div class="page-header">
<h1>Friends</h1>
</div>
<hr />
<% if @user_friendships.empty? %>
<em>No <%= params[:list] %> friends yet!</em>
<% end %>
<% @user_friendships.each do |friendship| %>
<% friend = friendship.friend %>
<div id="<%= dom_id(friendship) %>" class="friend panel">
<div class="panel-heading">
<span class="pull-right label>"><%= "#{friendship.state}".upcase %></span>
<h3 class="panel-title"><%= friend.full_name %></h3>
</div>
<div class="panel-body">
<div class="row">
<div class="col-md-1">Put gravatar url here</div>
<div class="col-md-11">
<em>Friends since time_ago_in_words ago</em>
</div>
</div>
</div>
<div class="panel-footer clearfix">
<%= link_to "Update friendship", edit_user_friendship_path( friend.profile_name), class: 'btn btn-primary pull-right' %>
</div>
</div>
<% end %>
这是用户友谊控制器：
class UserFriendshipsController < ApplicationController
before_filter :authenticate_user!
def index
@user_friendships = current_user.user_friendships.all
end
def new
if params[:friend_id]
@friend = User.where(profile_name: params[:friend_id]).first
raise ActiveRecord::RecordNotFound if @friend.nil?
@user_friendship = current_user.user_friendships.new(friend: @friend)
else
flash[:error] = "Friend required"
end
rescue ActiveRecord::RecordNotFound
render file: 'public/404', status: :not_found
end
def create
if params[:user_friendship] && params[:user_friendship].has_key?(:friend_id)
@friend = User.where(profile_name: params[:user_friendship][:friend_id]).first
@user_friendship = UserFriendship.request(current_user, @friend)
respond_to do |format|
if @user_friendship.new_record?
format.html do
flash[:error] = "There was a problem creating that friend request."
redirect_to profile_path(@friend)
end
format.json { render json: @user_friendship.to_json, status: :precondition_failed }
else
format.html do
flash[:success] = "Friend request sent to #{@friend.full_name}."
redirect_to profile_path(@friend.profile_name)
end
format.json { render json: @user_friendship.to_json }
end
end
else
flash[:error] = "Friend required"
redirect_to root_path
end
end
def edit
@friend = User.where(profile_name: params[:id]).first
@user_friendship = current_user.user_friendships.find(params[:id])
end
def destroy
@user_friendship = current_user.user_friendships.find(params[:id])
if @user_friendship.destroy
flash[:success] = "Friendship destroyed."
end
redirect_to user_friendships_path
end
def accept
@user_friendship = current_user.user_friendships.find(params[:id])
if @user_friendship.accept!
flash[:success] = "You are now friend with #{@user_friendship.friend.full_name}"
else
flash[:error] = "That friendship could not be accepted."
end
redirect_to user_friendships_path
end
def block
@user_friendship = current_user.user_friendships.find(params[:id])
if @user_friendship.block!
flash[:success] = "You have blocked #{@user_friendship.friend.full_name}."
else
flash[:error] = "That friendship could not be blocked."
end
redirect_to user_friendships_path
end
private
def friendship_association
case params[:list]
when nil
current_user.user_friendships
when 'blocked'
current_user.blocked_user_friendships
when 'pending'
current_user.pending_user_friendships
when 'requested'
current_user.requested_user_friendships
when 'accepted'
current_user.accepted_user_friendships
end
end
private
def user_friendship_attributes
params.require(:user_friendship).permit(:user, :friend, :user_id, :friend_id, :state)
end
end
最后，我将包含用户友谊模型：
class UserFriendship < ActiveRecord::Base
belongs_to :user
belongs_to :friend, class_name: 'User', foreign_key: 'friend_id'
state_machine :state, initial: :pending do
after_transition on: :accept, do: :send_acceptance_email
state :requested
event :accept do
transition any => :accepted
end
end
def self.request(user1, user2)
transaction do
friendship1 = create(user: user1, friend: user2, state: 'pending')
friendship2 = create(user: user2, friend: user1, state: 'requested')
friendship1.send_request_email
friendship1
end
end
def send_request_email
UserNotifier.friend_requested(id).deliver
end
def send_acceptance_email
UserNotifier.friend_request_accepted(id).deliver
end
def mutual_friendship
self.class.where({user_id: friend_id, friend_id: user_id}).first
end
# Manually updating the state to avoid callbacks and infinite loops
def accept_mutual_friendship
mutual_friendship.update_attribute(:state, 'accepted')
end
end
我知道我必须以某种方式改变这一点，但我不知道如何做到这一点。我希望此页面显示用户拥有的所有朋友，无论是处于已接受状态还是待处理状态。谁能看到我需要做什么？
谢谢！
编辑：如果我将views / user_friendships / index.html更改为 friend.full_name 而不是 @ friend.full_name ，我仍然会收到相同的错误。我可以验证当前在db中的用户是否都有一个有效的名字和姓氏（因此全名方法应该有效）。
另一个编辑：这是一个rails控制台条目，显示我在数据库中有用户友情：
2.1.2 :003 > UserFriendship.all
UserFriendship Load (0.3ms) SELECT "user_friendships".* FROM "user_friendships"
=> #<ActiveRecord::Relation [#<UserFriendship id: 1, user_id: 6, friend_id: nil, created_at: "2014-10-04 14:20:42", updated_at: "2014-10-04 14:20:42", state: nil>, #<UserFriendship id: 2, user_id: 6, friend_id: nil, created_at: "2014-10-04 14:21:32", updated_at: "2014-10-04 14:21:32", state: nil>, #<UserFriendship id: 3, user_id: 6, friend_id: 3, created_at: "2014-10-04 14:21:50", updated_at: "2014-10-04 14:21:50", state: nil>, #<UserFriendship id: 4, user_id: 6, friend_id: 6, created_at: "2014-10-04 14:23:58", updated_at: "2014-10-04 14:23:58", state: nil>, #<UserFriendship id: 5, user_id: 6, friend_id: 6, created_at: "2014-10-04 14:25:05", updated_at: "2014-10-04 14:25:05", state: nil>, #<UserFriendship id: 6, user_id: 6, friend_id: 4, created_at: "2014-10-04 14:25:15", updated_at: "2014-10-04 14:25:15", state: nil>, #<UserFriendship id: 7, user_id: 6, friend_id: 6, created_at: "2014-10-04 20:42:40", updated_at: "2014-10-04 20:42:40", state: nil>, #<UserFriendship id: 8, user_id: 6, friend_id: 6, created_at: "2014-10-04 20:45:44", updated_at: "2014-10-04 20:45:44", state: nil>, #<UserFriendship id: 9, user_id: 6, friend_id: 6, created_at: "2014-10-04 21:38:17", updated_at: "2014-10-04 21:38:17", state: nil>, #<UserFriendship id: 10, user_id: 6, friend_id: 6, created_at: "2014-10-09 16:53:44", updated_at: "2014-10-09 16:53:44", state: "pending">, ...]>
2.1.2 :004 >
另一个编辑：这是用户模型models / user.rb：
class User < ActiveRecord::Base
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
validates :first_name, presence: true
validates :last_name, presence: true
validates :profile_name, presence: true,
uniqueness: true,
format: {
with: /\A.+\z/,
message: "must be formatted correctly"
}
has_many :statuses
has_many :user_friendships
has_many :friends, -> { where user_friendships: { state: 'accepted'} }, through: :user_friendships
has_many :pending_user_friendships, -> { where state: 'pending' },
class_name: 'UserFriendship',
foreign_key: :user_id
has_many :pending_friends, through: :pending_user_friendships, source: :friend
def full_name
first_name + " " + last_name
end
def gravatar_url
stripped_email = email.strip
downcased_email = stripped_email.downcase
hash = Digest::MD5.hexdigest(downcased_email)
"http://gravatar.com/avatar/#{hash}"
end
end
答案 0 :(得分：0)
而不是@ friend.full_name使用friend.full_name
您已在此处定义＆lt;％friend = friendship.friend％＆gt;
答案 1 :(得分：0)
所以我很确定发生的事情是我的一些数据库表在我运行的rake db：migrate期间被删除了。我这样做是因为我正在寻找一个类似的rails应用程序，它正在构建社交网站并在两者之间来回切换我的数据库。不确定如何或为什么迁移删除的东西（我相信它删除了名字和姓氏，这就是为什么full_name将是一个零错误）。我将恢复到先前的提交，其中一切正常，并尝试从那里重建。
感谢帖子！
tl; dr：不要在不知道你在做什么的情况下运行db：migrate