Ruby:如何检查变量是否存在于散列定义中 [英] Ruby: how to check if variable exists within a hash definition
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问题描述
我是Ruby的新手。有没有办法做到以下几点?
hash = {
:key1 =>界定?值1? value1:无,
:key2 =>界定?值2? value2:nil
}
puts hash [:key1]#outputs:[expression]
以上代码存储表达式,而不是值(如果已定义)或 nil (如果未定义)。 c> Proc 。
hash = {
:key1 => lambda {defined?(value1)? value1:nil},
:key2 => lambda {defined?(value2)? value1:nil}
}
hash [:key1] .call
http://www.ruby- doc.org/core-1.9.2/Kernel.html#method-i-lambda
I'm new to Ruby. Is there a way to do the following?
hash = {
:key1 => defined? value1 ? value1 : nil,
:key2 => defined? value2 ? value2 : nil
}
puts hash[:key1] # outputs: ["expression"]
The above code stores the expression, instead of the value (if it is defined) or nil (if it is not defined).
解决方案
You're looking for lambda
, or Proc
.
hash = {
:key1 => lambda { defined?(value1) ? value1 : nil },
:key2 => lambda { defined?(value2) ? value1 : nil }
}
hash[:key1].call
http://www.ruby-doc.org/core-1.9.2/Kernel.html#method-i-lambda
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