Variable scope and modification

Question

Why does calling the mess_with_vars method not modify the value of the variables shown within?

def mess_with_vars(one, two, three)
  one = "two"
  two = "three"
  three = "one"
end

one = "one"
two = "two"
three = "three"

mess_with_vars(one, two, three)

puts "one is: #{one}"
puts "two is: #{two}"
puts "three is: #{three}"

Read this article - http://robertheaton.com/2014/07/22/is-ruby-pass-by-reference-or-pass-by-value/ — Wand Maker, Sep 01 '15 at 18:18

score 1 · Accepted Answer · edited May 23 '17 at 11:58

1

Ruby is pass-by-value (Is Ruby pass by reference or by value?), so you can definitely modify the value of objects, and you will see its effects outside a method.

Consider these:

def mess_with_vars(one, two, three)
  one.gsub!('one','two')
  two.delete!("wo")
  three.replace "one"
end

All above modify the arguments.

edited May 23 '17 at 11:58

Community

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answered Sep 01 '15 at 18:22

Filip Bartuzi

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sawa · Answer 2 · 2015-09-01T18:13:24.017

-1

Because the scope of a local variable initialized in a method definition is the method definition.

edited Sep 01 '15 at 18:13

answered Sep 01 '15 at 18:10

sawa

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I'd chalk it more up to pass-by-reference, no? – Dave Newton Sep 01 '15 at 18:12
Okay, so if these were instance variables I'd expect the variables to be modified? – Joe Ainsworth Sep 01 '15 at 18:18
@JoeAinsworth Sorry for the previous comment. Yes. Since it is in the main environment, you can access the modified instance variables outside of the method definition. – sawa Sep 01 '15 at 18:29

Variable scope and modification

2 Answers2

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