Rails 5: rails s与捆绑包exec rails s

Question

我第一次在Rails 5上启动了一个项目，我很好奇为什么在Rails 4上运行'rails s‘会运行得很好，但现在我在Rails 5上，为了正确运行命令，我需要在它前面加上'bundle exec’。

下面是我的Gemfile。同样，如果我在我所有的rails命令前面加上。我只是好奇是否有其他人经历过这种情况，或者是否有人能给我一些关于为什么会发生这种情况的见解？

 source 'https://rubygems.org'
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 5.0.0', '>= 5.0.0.1'
 # Use postgresql as the database for Active Record
 gem 'pg', '~> 0.18'
 # Use Puma as the app server
 gem 'puma', '~> 3.0'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5.0'
 # Use Uglifier as compressor for JavaScript assets
 gem 'uglifier', '>= 1.3.0'
 # Use CoffeeScript for .coffee assets and views
 gem 'coffee-rails', '~> 4.2'
 # See https://github.com/rails/execjs#readme for more supported runtimes
 # gem 'therubyracer', platforms: :ruby

 # Use jquery as the JavaScript library
 gem 'jquery-rails'
 # Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
 gem 'turbolinks', '~> 5'
 # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
 gem 'jbuilder', '~> 2.5'
 # Use Redis adapter to run Action Cable in production
 # gem 'redis', '~> 3.0'
 # Use ActiveModel has_secure_password
 # gem 'bcrypt', '~> 3.1.7'

 gem 'bootstrap', '~> 4.0.0.alpha3'
 source 'https://rails-assets.org' do
 gem 'rails-assets-tether', '>= 1.1.0'
 end
 gem "paperclip", "~> 5.0.0"
 gem "browser"
 # Use Capistrano for deployment
 gem 'capistrano-rails', group: :development

 group :development, :test do
 # Call 'byebug' anywhere in the code to stop execution and get a debugger console
 gem 'byebug', platform: :mri
 end

 group :development do
 # Access an IRB console on exception pages or by using <%= console %> anywhere in the code.
 gem 'web-console'
 gem 'listen', '~> 3.0.5'
   # Spring speeds up development by keeping your application running in the  background. Read more: https://github.com/rails/spring
   gem 'spring'
   gem 'spring-watcher-listen', '~> 2.0.0'
 end

 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
 gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

Answer 1

听起来你全局安装的rails命令是Rails4，这就是你所说的“它不能正常运行”的原因。当你运行bundle exec时，它会使用当前Gemfile中的rails命令，因为你的Gemfile中有rails 5，所以它可以正常工作。

我推荐使用RVM或rbenv，我个人喜欢RVM，因为它会自动切换到我的Gemfile中指定的ruby版本的gemset。

例如，当我用cd进入我的项目目录时，我得到如下消息：

Heroku使用你的Gemfile来选择

，这一切都很好-Heroku也是这样做的。

Answer 2

使用bundle exec可以保证程序在gemfile中指定的环境中运行，这意味着程序的创建者希望它在这个环境中运行，这意味着无论你的计算机上有什么奇怪的设置，它都应该正确运行。

参考：Use bundle exec rake or just rake?