gravatar_for 没有方法错误 哈特尔轨道 第 7 章

Question

一切都很好，直到我尝试定义gravatar_for并调用它。 user.email.downcase是零类。 以下是我正在使用的内容。 如果您需要任何其他信息，请告诉我。

我在网址http://localhost:3000/users/1运行本地主机时看到 NoMethodError in Users#show

`Showing /Users/nathandewaele/Desktop/workspce/static_pages/app/views/users/show.html.erb where line #6 raised:
undefined method `downcase' for nil:NilClass`

提取的源围绕第 5 行 gravatar_id = Digest::MD5::hexdigest(user.email.downcase)

`Rails.root: /Users/nathandewaele/Desktop/workspce/static_pages
Application Trace | Framework Trace | Full Trace
app/helpers/users_helper.rb:5:in `gravatar_for'
app/views/users/show.html.erb:6:in `_app_views_users_show_html_erb___4114710587947303689_70365956197180'
Request
Parameters:
{"id"=>"1"}
Toggle session dump
Toggle env dump
Response
Headers:
None`

app/helpers/users_helper.rb

```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
```

app/controllers/users_controller.rb

```ruby
class UsersController < ApplicationController
    def show
    @user = User.find(params[:id])
  end
  def new
        @user = User.new
  end
end
```

app/db/schema.rb

```ruby
ActiveRecord::Schema.define(version: 20171108202327) do
  create_table "users", force: :cascade do |t|
    t.string "name"
    t.string "email"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string "password_digest"
    t.index ["email"], name: "index_users_on_email", unique: true
  end
end
```

app/controllers/config/routes.rb

```ruby
Rails.application.routes.draw do
  # get '/new', to: 'users#new'
    get '/show', to: 'users#show'
    get  '/help', to: 'static_pages#help'
    get '/about', to: 'static_pages#about'
    get '/contact', to: 'static_pages#contact'
    get  '/signup',  to: 'users#new'
    resources :users
end
```

app/views/users/show.html.erb

```erb
<% provide(:title, @user.name) %>
<div class="row">
  <aside class="col-md-4">
    <section class="user_info">
      <h1>
        <%= gravatar_for @user %>
        <%= @user.name %>
      </h1>
    </section>
  </aside>
</div>
```

错误截图

Answer 1

有同样的问题，当我用代码更新/app/helpers/users_helper 时解决了：

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

(如清单 7.9 所示(

Answer 2

我遇到了同样的问题，很难追踪！如上所述，未向数据库发送电子邮件。在我更改了我混淆自己的模型/users.rb 文件中的代码后，我的问题似乎自行解决： before_save { self.email = email.downcase } .

在我使用before_save { self.email = email.downcase! }之前.验证位于 Rails 教程的第 6 章中。不知何故，我混淆了email.downcase！与self.email = email.downcase.

这仍然留下了一个谜团，为什么在没有电子邮件的情况下创建帐户，而不是阻止我继续的错误......