Ruby：如果存在变量，则使用最简洁的方式，否则使用默认值 [英] Ruby: Most concise way to use a variable if it exists, otherwise use default value

问题描述

在Ruby中，我试图编写一个使用变量的行，如果已设置，则默认为某个值：

  myvar =＃赋值给ENV ['MY_VAR']，否则赋值给'foobar'
  

<如果ENV ['MY_VAR']。is_set

  #w函数检查是否已设置
 myvar = ENV ['MY_VAR'] 
 else 
 myvar ='foobar'
 end 
  

但是这是比较冗长的，我试图用最简洁的方式写出来。我怎样才能做到这一点？

解决方案

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

N.B。这有点不正确（如果哈希值可以包含值 nil ），但由于 ENV 只包含字符串，它可能是好的够了。

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'

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

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

解决方案

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

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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