在 Ruby on Rails IRB 中停止加载脚本执行的最佳方法答案

【问题标题】：Best way to stop load script execution in Ruby on Rails's IRB在 Ruby on Rails IRB 中停止加载脚本执行的最佳方法
【发布时间】：2013-04-09 16:19:43
【问题描述】：

在 Ruby on Rails 的 IRB 中寻找退出已加载脚本的最佳方式。 Kernel.exit & Kernel.abort 会让你完全退出 IRB 会话。理想情况下，这将在某些条件条件下发生。

我的脚本/my_script.rb:

puts "My Script is running!"
# if some criteria, stop execution of this script without stoping IRB
puts "This will never happen"

理想的结果：

$ rails console
irb(main):001:0> load 'script/my_script.rb'
My Script is running!
irb(main):002:0>

【问题讨论】：

标签： ruby-on-rails ruby exit irb

【解决方案1】：

使用__END__ 关键字停止解析器。

puts "My Script is running!"
__END__
puts "This will never happen"
...

或者只是注释掉脚本的其余部分（如果您需要___END__ 之后的格式良好的DATA 流）

puts "My Script is running!"
=begin
puts "This will never happen"
...
=end

如果您需要基于逻辑而不是在固定点提前退出，您可以将脚本主体放在一个函数中并提前返回。

def do_work
  puts "My Script is running!"
  ...
  return if exit_condition?
  puts "This will never happen if exit condition is true"
  ...
end

do_work

或者，将您的脚本放在开始块中并挽救您引发的异常

begin
  puts "My Script is running!"
  raise SystemExit if exit_condition?
  puts "This will never happen if exit condition is true"
rescue SystemExit
end

【讨论】：

基于原始问题的有效答案。如果它应该有条件地退出，它将不起作用。（我已经更新了帖子以包含条件要求。）
@spyle 正在解决这个问题，请参阅更新。

【解决方案2】：

我现在能想到的最佳解决方案是引发脚本未处理的异常。但是，您会得到堆栈跟踪输出，这可能是不可取的。

脚本/my_script.rb

puts "My Script is running!"
raise "quiting, but I'm not happy about it"
puts "This will never happen"

结果：

irb(main):001:0> load 'script/my_script.rb'
My Script is running!
RuntimeError: quiting, but I'm not happy about it
    from script/my_script.rb:2:in `<top (required)>'
    from /usr/local/rbenv/versions/1.9.3-p374/lib/ruby/gems/1.9.1/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:245:in `load'
    from /usr/local/rbenv/versions/1.9.3-p374/lib/ruby/gems/1.9.1/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:245:in `block in load'
    from /usr/local/rbenv/versions/1.9.3-p374/lib/ruby/gems/1.9.1/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:236:in `load_dependency'
    from /usr/local/rbenv/versions/1.9.3-p374/lib/ruby/gems/1.9.1/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:245:in `load'
    from (irb):1
    from /usr/local/rbenv/versions/1.9.3-p374/lib/ruby/gems/1.9.1/gems/railties-3.2.13/lib/rails/commands/console.rb:47:in `start'
    from /usr/local/rbenv/versions/1.9.3-p374/lib/ruby/gems/1.9.1/gems/railties-3.2.13/lib/rails/commands/console.rb:8:in `start'
    from /usr/local/rbenv/versions/1.9.3-p374/lib/ruby/gems/1.9.1/gems/railties-3.2.13/lib/rails/commands.rb:41:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'
irb(main):002:0>

【讨论】：

你可以引发异常，然后拯救它，什么也不做。