为什么我的 Rails Server 无法启动？答案

【问题标题】：Why won't my Rails Server start?为什么我的 Rails Server 无法启动？
【发布时间】：2015-03-12 17:55:26
【问题描述】：

我今晚尝试启动我的 Rails 服务器，但没有成功。我对 ROR 很陌生。我收到以下错误：

=> Booting WEBrick
=> Rails 4.2.0 application starting in development on http://localhost:3000
=> Run `rails server -h` for more startup options
=> Ctrl-C to shutdown server
Exiting
/Users/HighlandMcKenna/.rvm/gems/ruby-2.2.0/gems/devise-3.1.2/lib/devise/rails/routes.rb:414:in `ensure in with_devise_exclusive_scope': undefined method `merge!' for #<ActionDispatch::Routing::Mapper::Scope:0x007ff0d6ae3728> (NoMethodError)
    from /Users/HighlandMcKenna/.rvm/gems/ruby-2.2.0/gems/devise-3.1.2/lib/devise/rails/routes.rb:414:in `with_devise_exclusive_scope'
    from /Users/HighlandMcKenna/.rvm/gems/ruby-2.2.0/gems/devise-3.1.2/lib/devise/rails/routes.rb:227:in `block (2 levels) in devise_for'
    from /Users/HighlandMcKenna/.rvm/gems/ruby-2.2.0/gems/devise-3.1.2/lib/devise/rails/routes.rb:330:in `block in devise_scope'
    from /Users/HighlandMcKenna/.rvm/gems/ruby-2.2.0/gems/actionpack-4.2.0/lib/action_dispatch/routing/mapper.rb:940:in `block in constraints'
    from /Users/HighlandMcKenna/.rvm/gems/ruby-2.2.0/gems/actionpack-4.2.0/lib/action_dispatch/routing/mapper.rb:816:in `scope'
    from /Users/HighlandMcKenna/.rvm/gems/ruby-2.2.0/gems/actionpack-4.2.0/lib/action_dispatch/routing/mapper.rb:940:in `constraints'

直到现在它每次都有效，我不知道为什么。请给我指导。

【问题讨论】：

你能用你的 Gemfile 更新你的问题吗？我认为您的设计版本需要更新。
Devise raises error with Rails 4.2 upgrade 的可能重复项

标签： ruby-on-rails

【解决方案1】：

这是一个我认为在 3.4.0 版本中已修复的问题

尝试将您的 gem 文件更新为

gem '设计', '~> 3.4.0'

然后运行

捆绑更新设计

【讨论】：