ruby 检查常量是否已定义
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时间：2020-09-06 05:00:52 来源:igfitidea点击:
Check if a constant is already defined
提问by peter
This is a simple one, I hope. How do I check, in the following example, if a constant is already defined?
这是一个简单的，我希望。在下面的示例中，如何检查常量是否已定义？
#this works
var = var||1
puts var
var = var||2
puts var
#this doesn't
CONST = CONST||1
puts CONST
CONST = CONST||2
puts CONST
=> 1
1
uninitialized constant CONST (NameError)
回答by jibiel
回答by rusllonrails
pry> User.const_defined?("PER_PAGE")
=> true
pry> User.const_defined?("PER_PAGE123")
=> false
回答by akostadinov
CONST ||= :default_value
the above works for me on ruby 1.9.3 but fails on 1.8... well 1.8 is ancient now.
以上在 ruby 1.9.3 上对我有效，但在 1.8 上失败......现在 1.8 很古老了。
