Re: Why does it work? (variable scope)

Clear. Thanks a lot to all.


2012/9/10 Robert Klemme <[e-mail]>:
> On Mon, Sep 10, 2012 at 4:57 PM, I=C3=B1aki Baz Castillo <[e-mail]> =
wrote:
>> Two similar cases (same behavior):
>>
>> 1)
>> ---------------------
>> my_var =3D 123  if false
>>
>> puts my_var
>> =3D> nil
>> ---------------------
>>
>> 2)
>> ---------------------
>> if false
>>   my_var =3D 123
>> end
>>
>> puts my_var
>> =3D> nil
>> ---------------------
>>
>> Somebody could expect that "puts my_var" should raise "NameError:
>> undefined local variable or method `my_var'" in both cases.
>
> The issue with expectations is that sometimes they aren't met. :-)
>
>> So I can understand that in case 1) the Ruby interpreter knows about
>> my_var variable since it reads it before checking the "if". But in
>> case 2) It seems that my_var variable is known when the script/file is
>> loaded since the interpreter will never run into the "if false"
>> statement.
>>
>> Am I right? Thanks a lot.
>
> Mostly.  The variable is known from the lexical position in the code
> where it is defined - even if that code is not executed - as you found
> out:
>
>> --------------------
>> puts "1: defined? my_var: #{(defined? my_var).inspect}"
>>
>> if false
>>   my_var =3D 123
>> end
>>
>> puts "2: defined? my_var: #{(defined? my_var).inspect}"
>>
>>
>> =3D>
>> 1: defined? my_var: nil
>> 2: defined? my_var: "local-variable"
>> --------------------
>
> That's also the reason why these behave differently although they seem
> to do the same:
>
> $ ruby -e 'if x.nil?; x=3D123; end; p x'
> -e:1:in `<main>': undefined local variable or method `x' for
> main:Object (NameError)
> $ ruby -e 'x=3D123 if x.nil?; p x'
> 123
>
> Kind regards
>
> robert
>
>
> --
> remember.guy do |as, often| as.you_can - without end
> http://blog.rubybestpractices.com/
>



--=20
I=C3=B1aki Baz Castillo
<[e-mail]>