控制器梅勒在Ruby on Rails的，活動記錄查詢

我遵循的軌道上建立一個郵件的紅寶石（指南的網站：https://launchschool.com/blog/handling-emails-in-rails）的指導。控制器梅勒在Ruby on Rails的，活動記錄查詢

我的預覽看起來是這樣的：sample_email.html.erb

<!DOCTYPE html> 
<html> 
<head> 
    <meta content='text/html; charset=UTF-8' http-equiv='Content-Type' /> 
</head> 
<body> 
<h1>Hi <%= @user.username %></h1> 
<p> 
Sie haben folgende Tags ausgewählt: 
    <% @user.tag_list.each do |tag| %> 
    <%= tag %> <br> 
    <% end %> 

    <br><br> 
    <% @infosall.each do |info| %> #<-- Problem on this line 
     <%= info.name %><br> 
    <% end %><br> 
</p> 
</body> 
</html>

@ user.username和@ user.tag_list得到呈現，但@infosall不會呈現。我需要在哪裏輸入@infosall，以便它在預覽中呈現？

example_mailer_preview.rb：

# Preview all emails at http://localhost:3000/rails/mailers/example_mailer 
class ExampleMailerPreview < ActionMailer::Preview 
    def sample_mail_preview 
    ExampleMailer.sample_email(User.last) 
    end 
end

example_mailer.rb：

class ExampleMailer < ApplicationMailer 
    default from: "" 

    def sample_email(user) 
    @user = user 
    mail(to: @user.email, subject: 'Sample Email') 

    end 
end

users_controller.rb：

class UsersController < ApplicationController 

    def show 
    @user = User.find_by_username(params[:username]) 
    @tags = @user.tag_list 
    @infosall = Array.new 
    @tags.each do |tag| 
     @infosall = @infosall + Info.tagged_with(tag) 
    end 

    @infosall.uniq! 
    @infosall.sort! { |a,b| b.created_at <=> a.created_at } 
    end 

end

編輯：當我做這example_mailer_preview.rb：

# Preview all emails at http://localhost:3000/rails/mailers/example_mailer 
class ExampleMailerPreview < ActionMailer::Preview 
    def sample_mail_preview 
    ExampleMailer.sample_email(User.last) 

     @user = User.last 
     @tags = @user.tag_list 
     @infosall = Array.new 
     @tags.each do |tag| 
      @infosall = @infosall + Info.tagged_with(tag) 
     end 

     @infosall.uniq! 
     @infosall.sort! { |a,b| b.created_at <=> a.created_at } 
    end 
end

我得到一個無方法錯誤：未定義的方法`find_first_mime_type」爲＃與此代碼：

def find_preferred_part(*formats) 
    formats.each do |format| 
    if part = @email.find_first_mime_type(format) 
     return part 
    end 
    end

我有什麼錯？任何建議？

來源

2016-02-13 Metaphysiker