Ruby 触发器什么时候有用?

问题描述

由于教程，我想我了解触发器的工作原理，但那里的示例仅用于教学.任何人都可以举一个例子说明你如何实际使用或将使用触发器?

I think I understand how a flip-flop works thanks to a tutorial, but the example there is contrived just for teaching. Can anyone give an example of how you have actually used or would use a flip-flop?

我正在寻找一个真实世界的应用程序，而不仅仅是另一个演示.这个工具可以解决什么问题?

I'm looking for a real-world application, not just another demonstration. What problems can this tool solve?

该链接曾经是 http://vision-media.ca/resources/ruby/ruby-flip-flop-or-range-operators，但现在似乎是垃圾邮件.

The link used to be http://vision-media.ca/resources/ruby/ruby-flip-flop-or-range-operators, but seems to be spam this days.

推荐答案

这是一个例子(取自 rubycentral.com 文章)，您可以在其中仅打印文件中的某些行:

Here's an example (taken from a rubycentral.com article) where you print out only certain lines from a file:

file = File.open("ordinal")
while file.gets
    print if ($_ =~ /third/) .. ($_ =~ /fifth/)
end

这里假设您有一个包含以下内容的文件:

This assumes that you have a file with the following contents:

first
second
third
fourth
fifth
sixth

程序只会打印出来:

third
fourth
fifth

这个想法是它的值在左侧事件发生之前为真，然后在右侧事件发生之前保持为真.如果使用得当，这可能是一个很好的语法糖，但您需要小心使内容可读.

The idea is that it the value is true until the left-hand event happens, and then stays true until the right-hand event happens. If used properly this can be a nice piece of syntactic sugar, but you need to be careful to make things readable.

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