Question

大家好，这个错误让我头疼了好几天，我真的不知道发生了什么。所以，我有两个模型：User和Composition。作品有belongs_to :user，用户有has_many :compositions和一个控制器，当我尝试从作曲家的所有者（用户）获取用户ID时，会出错。

错误

undefined method `id' for nil:NilClass

<%= link_to profile_path(compos.user.id), class: 'ui-btn btn-small' do %>
  <span class="icon-export"></span>visitar perfil</a>
<% end %>

组合物

class Composition < ApplicationRecord

  belongs_to :user

  validates :title, presence: true, :length => {maximum: 120}
  validates :description, presence: true

  has_attached_file :thumbnail
  validates_attachment_content_type :thumbnail, content_type: /\Aimage/
  validates_attachment_file_name :thumbnail, matches: [/png\Z/, /jpe?g\Z/]
  do_not_validate_attachment_file_type :thumbnail
end

用户

class User < ApplicationRecord

  has_many :compositions

  rolify

  devise :database_authenticatable, :omniauthable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  mount_uploader :avatar, AvatarUploader

  # Validações
  validates_integrity_of  :avatar
  validates_processing_of :avatar

  validates_format_of :username, :with => /[\w]+/
  validates_length_of :username, :in => (5..32)
  validates_uniqueness_of :username

  #Previne que o avatar tenha um tamanho maior de 2MB
  private
  def avatar_size_validation
    errors[:avatar] << "should be less than 2MB" if avatar.size > 2.megabytes
  end
end

控制器

class StaticPagesController < ApplicationController

  before_filter :authenticate_user!

  def index
    @compositions = Composition.all.order('created_at desc').limit(4)
  end
end

Answer 1

您可以设置条件以检查是否存在compos.user。

<% if compos.user %>

但是，我认为你正在开发环境

，似乎它的数据不一致

您需要确保每个composition user_id必须存在。

class Composition < ApplicationRecord

  belongs_to :user
  validates :user, presence: true
end

这样你永远不会与user_id = nil

合作

关联未定义的方法`id＆＃39;

1 个答案: