ruby variable name conflict with method name

Question

ruby code

def something
  p 'hellp something'
  'hello'
end

p something + 'xx'
p '-----------'
something = something + 'xx'

The last code run error:

test01.rb:11:in <main>': undefined method+' for nil:NilClass (NoMethodError)

This is my understanding of the last code:

ruby explain the code from left to right.
Ruby parser see 'something' first, then it will see '=' on the right. So, it think the 'something' as a variable and its value is nil.
Ruby parser will see the second 'something', but do not know this is a variable or a method. So, it looks up the same name variable or method. Then it find the nil value 'something'. " nil + 'xx' " this code run with error.

I do not know whether my understanding is correct.

please, use English on this resource.

Ilya
– Ilya

2016-09-08 09:52:15 +00:00
Commented Sep 8, 2016 at 9:52 — Ilya
– Ilya, Commented Sep 8, 2016 at 9:52
OK, I have use English on this resource, thank you.

xiaom zhong
– xiaom zhong

2016-09-09 02:13:40 +00:00
Commented Sep 9, 2016 at 2:13 — xiaom zhong
– xiaom zhong, Commented Sep 9, 2016 at 2:13
Yes, this is more or less what happens.

Sergio Tulentsev
– Sergio Tulentsev

2017-07-23 07:49:25 +00:00
Commented Jul 23, 2017 at 7:49 — Sergio Tulentsev
– Sergio Tulentsev, Commented Jul 23, 2017 at 7:49

Stephane Paquet · Accepted Answer · 2017-07-23 11:50:20Z

1

In ruby everything is a class.

The line that is messing up your code is something = something + 'xx' at this moment the compiler is going to mix up everything in the following sequence.

the first something is given the nil value (from the NilClass)
the second something at the right of the equal sign is no longer associated with the method something you previously defined but to the nil object that was defined at step #1.
then, and this is when the error is triggered, you try to perform an operation on a nil object that is not allowed in ruby.

answered Jul 23, 2017 at 11:50

Stephane Paquet

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