尝试加载gem 'uglifier‘时出错。(Bundler::GemRequireError)

Question

为什么我会得到这个错误？

shibly@mybox:~/blog$ rails server
/home/shibly/.gem/ruby/2.2.4/gems/bundler-1.11.2/lib/bundler/runtime.rb:80:in `rescue in block (2 levels) in require': There was an error while trying to load the gem 'uglifier'. (Bundler::GemRequireError)
    from /home/shibly/.gem/ruby/2.2.4/gems/bundler-1.11.2/lib/bundler/runtime.rb:76:in `block (2 levels) in require'
    from /home/shibly/.gem/ruby/2.2.4/gems/bundler-1.11.2/lib/bundler/runtime.rb:72:in `each'
    from /home/shibly/.gem/ruby/2.2.4/gems/bundler-1.11.2/lib/bundler/runtime.rb:72:in `block in require'
    from /home/shibly/.gem/ruby/2.2.4/gems/bundler-1.11.2/lib/bundler/runtime.rb:61:in `each'
    from /home/shibly/.gem/ruby/2.2.4/gems/bundler-1.11.2/lib/bundler/runtime.rb:61:in `require'
    from /home/shibly/.gem/ruby/2.2.4/gems/bundler-1.11.2/lib/bundler.rb:99:in `require'
    from /home/shibly/blog/config/application.rb:7:in `<top (required)>'
    from /home/shibly/.gem/ruby/2.2.4/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:78:in `require'
    from /home/shibly/.gem/ruby/2.2.4/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:78:in `block in server'
    from /home/shibly/.gem/ruby/2.2.4/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `tap'
    from /home/shibly/.gem/ruby/2.2.4/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `server'
    from /home/shibly/.gem/ruby/2.2.4/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
    from /home/shibly/.gem/ruby/2.2.4/gems/railties-4.2.5/lib/rails/commands.rb:17:in `<top (required)>'
    from bin/rails:9:in `require'
    from bin/rails:9:in `<main>

Answer 1

你应该运行以下命令在Ubuntu中安装NodeJS

sudo apt-get install nodejs

或者在OSX上运行此命令

brew install nodejs

Uglifier是一个JS包装器，它需要运行JS运行时或JS解释器。我会选择安装NodeJS。

Answer 2

在默认的Rails Gemfile中，gem 'therubyracer‘的行被注释掉了。如果你取消对它的注释，你会得到那个宝石，它应该可以工作。

来自"Getting Started with Rails"：

编译CoffeeScript和JavaScript资源压缩要求您的系统上有可用的JavaScript运行时，如果没有运行时，您将在资源编译过程中看到execjs错误。通常，Mac和Windows都安装了JavaScript运行时。Rails将therubyracer gem添加到新应用程序的注释行中生成的Gemfile中，如果需要，您可以取消注释。therubyrhino是为JRuby用户推荐的运行时，默认情况下会将其添加到JRuby下生成的应用程序的Gemfile中。您可以在ExecJS.

上调查所有受支持的运行时

Answer 3

创建数据库时出错。

问题是Node.js试图在脚本中没有sudo的情况下进行安装：

sudo apt-get install nodejs