为什么会出现错误：UsersController#create 中的 TypeError 无法将 String 转换为 Hash答案

【问题标题】：Why do I get the error: TypeError in UsersController#create can't convert String into Hash为什么会出现错误：UsersController#create 中的 TypeError 无法将 String 转换为 Hash
【发布时间】：2015-02-27 21:45:35
【问题描述】：

我正在尝试实现电子邮件功能，以便当有人注册时他们会收到电子邮件。我正在关注本指南：http://guides.rubyonrails.org/action_mailer_basics.html

但我得到了错误：

TypeError in UsersController#create
can't convert String into Hash

application_mailer.rb：

class ApplicationMailer < ActionMailer::Base
  default "from@example.com"
  layout 'mailer'
end

user_mailer.rb:

class UserMailer < ApplicationMailer
  default from: 'notifications@example.com'

  def welcome_email(user)
    @user = user
    @url  = 'http://localhost:3000/users/login'
    mail(to: @user.email, subject: 'Welcome to My Awesome Site')
  end
end

views/user_mailer/welcome_email.html.erb：

<!DOCTYPE html>
<html>
  <head>
    <meta content='text/html; charset=UTF-8' http-equiv='Content-Type' />
  </head>
    <body>
    <h1>Welcome to example.com, <%= @user.name %></h1>
    <p>
      You have successfully signed up to example.com,
      your username is: <%= @user.login %>.<br>
    </p>
    <p>
      To login to the site, just follow this link: <%= @url %>.
    </p>
    <p>Thanks for joining and have a great day!</p>
  </body>
</html>

views/user_mailer/welcome_email.txt.erb

Welcome to example.com, <%= @user.name %>
===============================================

You have successfully signed up to example.com,
your username is: <%= @user.login %>.

To login to the site, just follow this link: <%= @url %>.

Thanks for joining and have a great day!

还有users_controller中的create方法：

def create
  @user = User.new(user_params)
if @user.save
  # login is achieved by saving a user's 'id' in a session variable, 
  # accessible to all pages
   UserMailer.welcome_email(@user).deliver_later
  session[:user_id] = @user.id
  redirect_to films_path
else
  render action: "new"
end
end

用户控制器中的用户参数：

def user_params 
    params.require(:user).permit(:password, :password_confirmation, :role, :first_name, :last_name, :house_no, :street, :town, :postcode, :email, :date_of_birth) 
end

完全错误：

TypeError in UsersController#create
can't convert String into Hash
Extracted source (around line #0):           

Rails.root: C:/Sites/Thor/Under Construction/ThorCinema/new/Lab/ThorCinema
Application Trace | Framework Trace | Full Trace

app/mailers/application_mailer.rb:2:in `<class:ApplicationMailer>'
app/mailers/application_mailer.rb:1:in `<top (required)>'
app/mailers/user_mailer.rb:1:in `<top (required)>'
app/controllers/users_controller.rb:33:in `create'

有人可以帮忙吗。

【问题讨论】：

您使用的是哪个 Rails 版本？如果您使用的是 rails 3，那么您不能传递 @user 这样，您必须传递 @user.id 然后从您的邮件中加载用户。
我使用的是 Rails 4.2.0
你能显示user_params，还有其余的错误。就像哪个数字确切提到该字符串不能转换为哈希
@Coderhs 我添加了user_params 和错误

标签： ruby-on-rails ruby ruby-on-rails-3 email methods

【解决方案1】：

default 引用 ActionMailer 中的哈希

所以这一行是不正确的，因为它指定了一个字符串而不是一个哈希

default "from@example.com"

应该是

default sender: "from@example.com"

请参阅

中的“默认哈希”部分

http://api.rubyonrails.org/classes/ActionMailer/Base.html

编辑

请注意，您的完整跟踪甚至为您指出了这条线......

app/mailers/application_mailer.rb:2:in `'

【讨论】：