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This tutorial explains about the variable is defined and initialized with a value.
In Ruby language, the Variable is declared and assigned with values.
Check if the variable is defined in Ruby
Ruby provides defined method.
It checks an expression to check whether it is a variable or assignment or expression or method.
If it is not unable to resolve, returns empty or nil.
number = 11
puts defined?(number)## returns local-variable
obj = {}
puts defined?(obj) ## returns local-variable
str = nil
puts defined?(str) ## returns local-variable
puts defined?(notdeclaredvariable) ## returns empty
puts defined?(@num=1)## returns assignment
puts defined?(def m; end) ## returns expression
Output:
local-variable
local-variable
local-variable
assignment
expression
You can also check conditional if expression to return true or false
number = 11
if (defined?(number)).nil?
puts "number is not defined\n"
else
puts "number is defined\n"
end
Similarly, you can use unless to check a variable is not defined.
unless defined? number1
puts "number1 is undefined"
end
