ruby-on-rails - 未定义的辅助方法

Question

我有一个问题:

undefined method `avatar_url' for #<User:0x000000040783a8>

Controller :

class ApplicationController < ActionController::Base
  protect_from_forgery
  helper :all
  helper_method :avatar_url

  protected

  def avatar_url(user)
    if user.avatar_url.present?
      user.avatar_url
    else
      default_url = "#{root_url}images/guest.png"
      gravatar_id = Digest::MD5.hexdigest(user.email.downcase)
      "http://gravatar.com/avatar/#{gravatar_id}.png?s=48&d=#{CGI.escape(default_url)}"
    end
  end
end

在 View 中:

...
<%for user in @users %>
  <%= image_tag avatar_url(user) %>, username: <%= user.username %>, e-mail: <%= user.email %>
<% end %>
...

有人帮帮我吗？

Answer 1

关键是错误信息:

undefined method `avatar_url' for #<User:0x000000040783a8>

错误不是因为辅助方法未定义:错误消息表明它是 User 类中缺少的方法。 ApplicationController 中定义的方法尝试:

def avatar_url(user)
  if user.avatar_url.present?
    user.avatar_url
  #...

您需要确保 User 类有一个 avatar_url 实例方法。