小编Chi*_*tra的帖子

在线下没有.2,我收到此错误:

Errno :: ENOENT in OrdersController #print

def generate_receipt(filename = nil, current_user = nil)
    filename ||= "public/receipts/#{id}.pdf"
    Prawn::Document.generate(filename, :page_layout => :portrait, :page_size => 'LETTER', :skip_page_creation => false, :top_margin => 50, :left_margin => 50)do |pdf|

      pdf_receipt_data(pdf, false, 'store_front', current_user)

      pdf.number_pages "<page> of <total>", :at => [0, 0]

    end
end

在我的localhost上这段代码正在运行但是在测试env时我收到了这个错误.我正在使用rails 4.2.
请帮帮我.

rvm list gemsets 显示安装rvm gemsets列表和

rvm gemset list 显示特定选定rvm gemsets的gemset列表.

这是正确的解释吗？

请帮我清除这意味着正确的解释,何时使用以及它如何有用？

感谢您的输入.

我使用数据库作为postgresql复制应用程序,但后来我知道应用程序正在使用mongodb,我得到了json格式的应用程序的转储,这是mongodb.

因此,有关将mongo db转储迁移到postgresql的任何帮助都将非常感激.

谢谢!

我在打开时遇到这个问题 -> rails 控制台

[chitra@localhost todo_app]$ rails c
/home/chitra/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/fileutils.rb:252:in `mkdir': Permission denied @ dir_s_mkdir - /run/user/gui/spring (Errno::EACCES)
    from /home/chitra/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/fileutils.rb:252:in `fu_mkdir'
    from /home/chitra/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/fileutils.rb:226:in `block (2 levels) in mkdir_p'
    from /home/chitra/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/fileutils.rb:224:in `reverse_each'
    from /home/chitra/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/fileutils.rb:224:in `block in mkdir_p'
    from /home/chitra/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/fileutils.rb:210:in `each'
    from /home/chitra/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/fileutils.rb:210:in `mkdir_p'
    from /home/chitra/.rvm/gems/ruby-2.2.0@todo/gems/spring-1.4.0/lib/spring/env.rb:37:in `tmp_path'
    from /home/chitra/.rvm/gems/ruby-2.2.0@todo/gems/spring-1.4.0/lib/spring/env.rb:54:in `pidfile_path'
    from /home/chitra/.rvm/gems/ruby-2.2.0@todo/gems/spring-1.4.0/lib/spring/env.rb:69:in `server_running?'
    from /home/chitra/.rvm/gems/ruby-2.2.0@todo/gems/spring-1.4.0/lib/spring/client/run.rb:25:in `call'
    from /home/chitra/.rvm/gems/ruby-2.2.0@todo/gems/spring-1.4.0/lib/spring/client/command.rb:7:in `call'
    from /home/chitra/.rvm/gems/ruby-2.2.0@todo/gems/spring-1.4.0/lib/spring/client/rails.rb:24:in `call'
    from /home/chitra/.rvm/gems/ruby-2.2.0@todo/gems/spring-1.4.0/lib/spring/client/command.rb:7:in `call'
    from /home/chitra/.rvm/gems/ruby-2.2.0@todo/gems/spring-1.4.0/lib/spring/client.rb:28:in `run'
    from /home/chitra/.rvm/gems/ruby-2.2.0@todo/gems/spring-1.4.0/bin/spring:49:in `<top (required)>'
    from /home/chitra/.rvm/gems/ruby-2.2.0@todo/gems/spring-1.4.0/lib/spring/binstub.rb:11:in `load'
    from /home/chitra/.rvm/gems/ruby-2.2.0@todo/gems/spring-1.4.0/lib/spring/binstub.rb:11:in `<top (required)>'
    from /opt/projects/todo_app/bin/spring:13:in `require'
    from …

在创建类时,我们使用关键字class:

class Abc
  Z = 5
  def add
    puts "anything here"
  end
end

在控制台中, Abc.class # => Class

Abc内部如何成为一个班级？class和之间有什么区别Class？

如果有人能够解释内部调用类常量和方法的方式,并且如果没有定义方法,那么我们将如何获得异常将会很棒"undefined class method".它背后的内在逻辑是什么？