Can you access Ruby variables with outer scope inside of methods?

Question

I'm learning Ruby and practicing by writing a Caesar cipher. Here's my code so far:

print "Enter rotation: "
rotation = gets.chomp
print "Enter string to encrypt: "
string = gets.chomp

def encrypt
    keys = (' '..'z').to_a
    values = (' '..'z').to_a.rotate(rotation)
    hash = Hash[keys.zip(values)]
    chars = string.split('')
    encrypted_chars = chars.collect { |char| hash[char] }
    encryptd_string = encrypted_chars.join
end

puts "Encrypted string: " + encrypt

It's saying that I don't have access to the rotation variable inside of the encrypt method. NameError: undefined local variable or method 'rotation' for main:Object.

From what I understand, rotation is a local variable with outer scope, and should be accessible inside of the encrypt method. Obviously something is wrong with that reasoning, so could someone explain what's wrong?

Possible duplicate of [Ruby accessing outer variables in nested function](https://stackoverflow.com/questions/1016408/ruby-accessing-outer-variables-in-nested-function) — ggorlen, Jul 28 '18 at 03:34

score 5 · Accepted Answer · answered May 09 '14 at 06:40

5

This is a duplicate of Ruby accessing outer variables in nested function.

You could make it an instance variable on the containing object by calling it @rotation, but why not just pass string and rotation into the encrypt method?

answered May 09 '14 at 06:40

Buck Doyle

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I could pass the parameters to the `encrypt` method, I was just looking for the simplest solution. – Adam Zerner May 09 '14 at 06:44
So what about this: `def outer def inner end end` Could you access `outer`'s variables in `inner`? – Adam Zerner May 09 '14 at 06:45
No, you can’t; see the link I put in the answer. – Buck Doyle May 09 '14 at 06:46

score 2 · Answer 2 · edited May 23 '17 at 12:23

The reason for this behaviour is that Local variables exist in a local scope and defining a method creates a new local scope for that method. Local varables are only visible in the current scope.

I was confused by this and found that relating the OP's question to one of nested methods only added confusion. But I've done a bit more research and discovered this succinct question and, in particular, this answer that explains it clearly as well as demonstrating a way to define a method without creating a new scope.

(I'm just adding this answer for the benefit of others because my search for an answer led me to this question.)

Can you access Ruby variables with outer scope inside of methods?

2 Answers2