Ruby:使用ENV变量(如果存在)的最简洁方法，否则使用默认值 [英] Ruby: Most concise way to use an ENV variable if it exists, otherwise use default value

问题描述

在Ruby中，我试图编写一条使用变量的行(如果已设置)，否则默认为某个值:

In Ruby, I am trying to write a line that uses a variable if it has been set, otherwise default to some value:

myvar = # assign it to ENV['MY_VAR'], otherwise assign it to 'foobar'

我可以这样编写这段代码:

I could write this code like this:

if ENV['MY_VAR'].is_set? #whatever the function is to check if has been set
  myvar = ENV['MY_VAR']
else
  myvar = 'foobar'
end

但是这很冗长，我正在尝试以最简洁的方式编写它.我该怎么办?

But this is rather verbose, and I'm trying to write it in the most concise way possible. How can I do this?

推荐答案

myvar = ENV['MY_VAR'] || 'foobar'

这有点不正确(如果散列可以包含值nil)，但是由于ENV仅包含字符串，因此可能就足够了.

N.B. This is slightly incorrect (if the hash can contain the value nil) but since ENV contains just strings it is probably good enough.

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