Take name of variable as input and output its value - Ruby

Question

I'd like to know if there is something Ruby that does something like this:

@my_var = "foo"
some_function_i_dont_know_name_of("@my_var")
 => "foo"

eval could potentially be used for code injections, if the value of @my_var can be set from the outside. instance_variable_get is safer. — Eneroth3
– Eneroth3, Commented May 23, 2019 at 13:55

Community · Accepted Answer · 2020-06-20 09:12:55Z

5

Seems like you are looking for instance_variable_get. From the docs:

Returns the value of the given instance variable, or nil if the instance variable is not set. The @ part of the variable name should be included for regular instance variables. Throws a NameError exception if the supplied symbol is not valid as an instance variable name. String arguments are converted to symbols.
class Fred
  def initialize(p1, p2)
    @a, @b = p1, p2
  end
end
fred = Fred.new('cat', 99)
fred.instance_variable_get(:@a)    #=> "cat"
fred.instance_variable_get("@b")   #=> 99

edited Jun 20, 2020 at 9:12

CommunityBot

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answered May 23, 2019 at 13:46

spickermann

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Comments

Ursus · Accepted Answer · 2019-05-23 13:53:33Z

2

Yes, there is.

@my_var = "foo"
instance_variable_get("@my_var")
 => "foo"

edited May 23, 2019 at 13:53

answered May 23, 2019 at 13:46

Ursus

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