Checking if a variable is defined in Ruby

How do you check whether a variable is defined in Ruby? Is there an "isset"-type method available?

From stackoverflow

• defined?(your_var) will work. Depending on what you're doing you can also do something like your_var.nil?

• use defined? It will return a string with the kind of the item or nil if it don't exist

  irb(main):007:0> a = 1
  => 1
  irb(main):008:0> defined? a
  => "local-variable"
  irb(main):009:0> defined? b
  => nil
  irb(main):010:0> defined? String
  => "constant"
  irb(main):011:0> defined? 1
  => "expression"
  

• this is useful if you want to do nothing if it does exist but create it if it doesn't exist

  def get_var
    @var ||= SomeClass.new()
  end
  

  this only creates the new class once after that just keeps returning the var

• Here is some code, nothing rocket science but it works well enough

  require 'rubygems'
  require 'rainbow'
  if defined?(var).nil?
   print "var is not defined\n".color(:red)
  else
   print "car is defined\n".color(:green)
  end