# Questionable behavior

**URL:** <https://www.ruby-forum.com/t/questionable-behavior/95285>\
**Category:** Ruby\
**Created:** [May 26, 2006, 3:55pm UTC](https://www.ruby-forum.com/t/questionable-behavior/95285 "2006-05-26T15:55:14Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [May 26, 2006, 3:55pm UTC](https://www.ruby-forum.com/t/questionable-behavior/95285/1 "2006-05-26T15:55:14Z")

</div>

I’m getting some very strange behavior from a conditional statement –  
I can;t imagine how it is happeneing and I wondering if I stumbled upon  
some sort of bug in Ruby. Although I have no idea how it could even  
occuer, perhaps someone else can see it. Here’s the code:

p pkg  
p pkg.gem  
p pkg.gem  
if pkg.gem  
p “HERE”  
pkg = pkg. **merge** ( pkg.gem )  
end  
p pkg

This prints

#\<OpenObject…\>  
nil  
nil  
nil

Notice it does not print “HERE” yet by that last print pkg has somehow  
become nil! Note that I repeated ‘p pkg.gem’ to show that it has  
nothing to do with calling this statment. Now if I remark out the pkg  
assignment:

p pkg  
p pkg.gem  
p pkg.gem  
if pkg.gem  
p “HERE”  
#pkg = pkg. **merge** ( pkg.gem )  
end  
p pkg

I get

#\<OpenObject…\>  
nil  
nil  
#\<OpenObject…\>

As it should be. How is this possible?

FYI  
Ubuntu Linux  
ruby 1.8.4 (2005-12-24) [i486-linux]

Thanks,  
T.

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<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [May 26, 2006, 4:58pm UTC](https://www.ruby-forum.com/t/questionable-behavior/95285/2 "2006-05-26T16:58:41Z")

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On May 26, 2006, at 9:54 AM, removed\_email\_address@domain.invalid wrote:

> ```
> p "HERE"
> 
> #pkg = pkg. __merge__ ( pkg.gem )
> 
> ```
> 
> As it should be. How is this possible?  
> I’d be happy to test it here and see if I can replicate it. But I  
> don’t know what an OpenObject is.  
> -Mat

---

<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [May 26, 2006, 5:05pm UTC](https://www.ruby-forum.com/t/questionable-behavior/95285/3 "2006-05-26T17:05:34Z")

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Hi,

On Fri, 26 May 2006 15:54:21 +0200, [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> I’m getting some very strange behavior from a conditional statement –  
> I can;t imagine how it is happeneing and I wondering if I stumbled upon  
> some sort of bug in Ruby. Although I have no idea how it could even  
> occuer, perhaps someone else can see it. Here’s the code:

No, that is no bug, it’ a feature 😉

here pkg is a method call

> p pkg  
> p pkg.gem  
> p pkg.gem  
> if pkg.gem  
> p “HERE”  
> after this line pkg is a local variable (because you assign to it)  
> pkg = pkg. **merge** ( pkg.gem )  
> end  
> unintialized local variables default to nil, so it prints nil  
> p pkg
> 
> This prints
> 
> #\<OpenObject…\>  
> nil  
> nil  
> nil

If you want the method call you can use pkg().

Here is another example:

$ cat lvar\_tst.rb  
def a  
“method”  
end

def test  
p a  
p a()  
if false  
a = 23  
end  
p a  
p a()  
end

test  
$ ruby lvar\_tst.rb  
“method”  
“method”  
nil  
“method”

This is just the way Ruby (it’s parser) handles local variables, but I  
think matz said that this will be made more “consistent” in future  
versions (i.e. if something is a lvar at some point in a scope it will  
be  
an lvar everywhere in this scope and you might get a warning for your  
above code, like “use of lvar before initialization”)

Hope that helps,  
Dominik

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<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [May 26, 2006, 5:34pm UTC](https://www.ruby-forum.com/t/questionable-behavior/95285/4 "2006-05-26T17:34:00Z")

</div>

It would be tricky to run the test in that the code is pretty deep  
inside my application. If your willing though I would be happy to send  
you the whole package to try. FYI, it’s the Reap project.

OpenObject is similar to OpenStruct and can be found in Ruby F.s.

Thanks,  
T.

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**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [May 26, 2006, 5:49pm UTC](https://www.ruby-forum.com/t/questionable-behavior/95285/5 "2006-05-26T17:49:47Z")

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Dominik B. wrote:

> > I’m getting some very strange behavior from a conditional statement –  
> > I can;t imagine how it is happeneing and I wondering if I stumbled upon  
> > some sort of bug in Ruby. Although I have no idea how it could even  
> > occuer, perhaps someone else can see it. Here’s the code:
> 
> No, that is no bug, it’ a feature 😉

Oh, I love those kind of “features”… NOT!

> This is just the way Ruby (it’s parser) handles local variables, but I  
> think matz said that this will be made more “consistent” in future  
> versions (i.e. if something is a lvar at some point in a scope it will be  
> an lvar everywhere in this scope and you might get a warning for your  
> above code, like “use of lvar before initialization”)

Why does it do this and why is that a good solution? How unintuitive  
can it possibly be? Why doesn’t it just convert the refernce to a lvar  
when it evaluates? Why does the parser have to look ahead and  
pre-judge the reference. You got code evaluating in a false condition  
–so anti-dynamic!

Sigh. Okay so referncing it as a local var --EVEN IN UNEVALUATED CODE  
changes a refernce to a local variable. Great! I was trying to take  
advantage of the isomorphism of local vars and metods --which I thought  
WAS a feature. So much for that.

Thanks Dominik,  
T.

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<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [May 26, 2006, 5:56pm UTC](https://www.ruby-forum.com/t/questionable-behavior/95285/6 "2006-05-26T17:56:21Z")

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Ah, despite my rant, there is an easy solution. And it makes it very  
clear the oddness of the way Ruby parser work here:

```
  if pkg.gem
    pkg = pkg. __merge__ ( pkg.gem )
  else
    pkg = pkg
  end

```

It won’t work without the ‘pkg = pkg’.

T.

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<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [May 26, 2006, 6:59pm UTC](https://www.ruby-forum.com/t/questionable-behavior/95285/7 "2006-05-26T18:59:24Z")

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Sounds like it’s pretty wrapped up. Interesting fix. And something  
to keep in mind for later. Hopefully later version of ruby will  
print warnings on this sort of thing.  
-Mat