ActionView::Template::Error: undefined method `email' for nil:NilClass

Question

我是 Rails 的新手，正在编写 Michael Hartl 的教程。我在第 7 章，一切都测试得很好，直到我……说实话，我不知道。一秒钟没问题，然后我添加了 gravatar_for，现在我失败了。我在这里四处寻找答案，有些人提到把 !在 downcase 之后不起作用。这是我收到的错误消息。我知道它就在我面前，但在花了两天时间之后，我觉得这是下一步。当我运行 bundle exec rake test 我收到这个：

ERROR["test_should_get_about", StaticPagesControllerTest, 2015-09-09 15:14:50 +0000]
 test_should_get_about#StaticPagesControllerTest (1441811690.06s)
ActionView::Template::Error:         ActionView::Template::Error: undefined method `email' for nil:NilClass
        app/helpers/users_helper.rb:5:in `gravatar_for'
        app/views/static_pages/about.html.erb:13:in `_app_views_static_pages_about_html_erb__2581941383523300906_55646340'
        test/controllers/static_pages_controller_test.rb:22:in `block in <class:StaticPagesControllerTest>'
    app/helpers/users_helper.rb:5:in `gravatar_for'
    app/views/static_pages/about.html.erb:13:in `_app_views_static_pages_about_html_erb__2581941383523300906_55646340'
    test/controllers/static_pages_controller_test.rb:22:in `block in <class:StaticPagesControllerTest>'

20/20: [======] 100% Time: 00:00:00, Time: 00:00:00

这是我的 app/helpers/user_helper.rb

module UsersHelper

# Returns the Gravatar for the given user.
def gravatar_for(user, options = { size: 80 })
gravatar_id = Digest::MD5::hexdigest(user.email.downcase)
size = options[:size]
gravatar_url = "https://secure.gravatar.com/avatar/#{gravatar_id}?s=#{size}"
image_tag(gravatar_url, alt: user.name, class: "gravatar")
end
end

这是我的 app/views/static_pages/about.html.erb

<% provide(:title, "About") %>
<h1>About</h1>
<p>
The <a href="http://www.railstutorial.org/"><em>Ruby on Rails
Tutorial</em></a> is a
<a href="http://www.railstutorial.org/book">book</a> and
<a href="http://screencasts.railstutorial.org/">screencast series</a>
to teach web development with
<a href="http://rubyonrails.org/">Ruby on Rails</a>.
This is the sample application for the tutorial.
</p>

<%= gravatar_for User.first, size: 50 %>
<%= gravatar_for User.first, size: 200 %>
<%= gravatar_for User.first, size: 80 %>
<%= gravatar_for User.first %>

这是我的 test/controllers/static_pages_controller_test.rb

require 'test_helper'

class StaticPagesControllerTest < ActionController::TestCase

def setup
@base_title = "Ruby on Rails Tutorial Sample App"
end


test "should get home" do
get :home
assert_response :success
assert_select "title", "Ruby on Rails Tutorial Sample App"  end

test "should get help" do
get :help
assert_response :success
assert_select "title", "Help | #{@base_title}"
end

test "should get about" do  
get :about
assert_response :success
assert_select "title", "About | #{@base_title}"
end

test "should get contact" do
get :contact
assert_response :success
assert_select "title", "Contact | #{@base_title}"
end
end

非常感谢任何帮助！

Answer 1

在您的 about.html.erb 中您有代码：

<%= gravatar_for User.first, size: 50 %>
<%= gravatar_for User.first, size: 200 %>
<%= gravatar_for User.first, size: 80 %>
<%= gravatar_for User.first %>

这将尝试从数据库中读取并找到第一个用户。该用户似乎不存在，我不记得 rails 教程中有该代码（如果有误，请纠正我）。静态页面测试应该独立于任何用户，我不明白为什么你首先想要关于站点上的用户图片:)

简而言之：删除提到的代码，它应该运行没问题。

Answer 2

您的测试数据库中没有用户，因此在尝试呈现

时 User.first 是 nil

<%= gravatar_for User.first, size: 50 %>

nil 因此作为 user 传递给 gravatar_for 助手，后者调用 email 方法：

gravatar_id = Digest::MD5::hexdigest(user.email.downcase)

这会导致错误。

解决方案：

确保 user 存在于 gravatar_for 助手中。
用至少一个用户填充你的测试数据库。

ActionView::Template::Error: undefined method `email' for nil:NilClass

ActionView::Template::Error: undefined method `email' for nil:NilClass

ruby-on-rails

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