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Ruby defined operator

defined? operator

The defined? the operator is used to check whether or not the passed expression is defined. It returns nil if its argument is not defined, otherwise, it returns a descriptive string of that argument.

Syntax :

defined? expression 

Here are some usage of defined? operator:

Example: Ruby defined operator

x =  1
Height = 100
puts ("defined operator in Ruby")
puts defined? x               # "local-variable"
puts defined? 12              # "expression"
puts defined? y               # nil
puts defined? puts            # "method"
puts defined? Height          # "constant"
puts defined? $&              # nil
puts defined? $_              # "global-variable"
puts defined? Math::PI        # "constant"
puts defined?( c = 22 )       # "assignment"
puts defined? 12.abs          # "method"

Output:

defined operator in Ruby
local-variable
expression

method
constant

global-variable
constant
assignment
method

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