检查是否已定义常量

Question

我希望这是一个简单的问题.在下面的示例中,如何检查是否已定义常量？

#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)

Answer 1

CONST = 2 unless defined? CONST

有关优秀操作员的更多信息,请参见此处defined?.

^{PS并且在未来我想你会想要var ||= 1而不是var = var||1.}

Answer 2

const_defined？API __CODE__