# Global not evaluated properly in 'if' statement modifier

**URL:** <https://www.ruby-forum.com/t/global-not-evaluated-properly-in-if-statement-modifier/63022>\
**Category:** Ruby\
**Created:** [June 10, 2006, 8:16pm UTC](https://www.ruby-forum.com/t/global-not-evaluated-properly-in-if-statement-modifier/63022 "2006-06-10T20:16:18Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [June 10, 2006, 8:16pm UTC](https://www.ruby-forum.com/t/global-not-evaluated-properly-in-if-statement-modifier/63022/1 "2006-06-10T20:16:18Z")

</div>

Hello all,

I am scratching my head over this one.  
I have a method:

def dispatchFile(file)  
song = Convert.new(file)  
case type  
when ‘ogg’  
song.oggToWav  
song.wavToOgg if $outtype == ‘ogg’  
song.wavToMp3 if $outtype == ‘mp3’  
song.wavToM4b if $outtype == ‘m4b’  
song.wavToFlac if $outtype == ‘flac’  
when ‘mp3’  
\<etc…\>  
end  
end

When I run this code the 'if’s are never evaluated. That is, I have  
printed  
$outtype, and it has a valid value, but the second method which matches  
the  
value never runs. If I comment out the ‘if’ and run the two methods  
manually  
it works fine.

In my tests $outtype’s value is ‘mp3’, so why doesn’t song.wavToMp3 run?  
What am I missing?

Thanks for consideration,  
-d

---

<div class="post-metadata">

**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [June 10, 2006, 8:59pm UTC](https://www.ruby-forum.com/t/global-not-evaluated-properly-in-if-statement-modifier/63022/2 "2006-06-10T20:59:57Z")

</div>

quoth the darren kirby:

> Hello all,
> 
> I am scratching my head over this one.  
> I have a method:

Well, nevermind. It is sorted.  
The docs for GetOptLong have usage examples like so:  
value = arg.inspect

So I got rid of the ‘inspect’ and now it works.

-d

---

<div class="post-metadata">

**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [June 10, 2006, 8:59pm UTC](https://www.ruby-forum.com/t/global-not-evaluated-properly-in-if-statement-modifier/63022/3 "2006-06-10T20:59:45Z")

</div>

On Jun 10, 2006, at 19:13, darren kirby wrote:

> ```
> song.wavToOgg if $outtype == 'ogg'
> 
> ```
> 
> $outtype, and it has a valid value, but the second method which  
> matches the  
> value never runs. If I comment out the ‘if’ and run the two methods  
> manually  
> it works fine.
> 
> In my tests $outtype’s value is ‘mp3’, so why doesn’t song.wavToMp3  
> run?  
> What am I missing?

I’m not able to generalise this result, my similar code (at bottom)  
works as it should.

So, at a guess, I’d suggest that $outtype is not actually “mp3” but  
is “mp3\n”. #puts is smart enough not to include an extra \n, and if  
you’re using #print, then the extra line break may not be obvious,  
since it would look just like the result of #puts. Similarly, "mp3 "  
wouldn’t display as obviously wrong.

For example:

irb(main):020:0\> foo = “mp3\n”  
irb(main):021:0\> puts foo.inspect  
“mp3\n”  
=\> nil  
irb(main):022:0\> puts foo  
mp3  
=\> nil  
irb(main):023:0\> foo == ‘mp3’  
=\> false

If that’s not the case, then I’m stumped.

matthew smillie.

[this code works]

def foobar  
type = ‘ogg’  
case type  
when ‘ogg’  
puts “\*always”  
puts “\*ogg” if $outtype == ‘ogg’  
puts “\*mp3” if $outtype == ‘mp3’  
end  
end  
=\> nil  
foobar  
\*always  
\*mp3  
=\> nil

---

<div class="post-metadata">

**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [June 10, 2006, 9:56pm UTC](https://www.ruby-forum.com/t/global-not-evaluated-properly-in-if-statement-modifier/63022/4 "2006-06-10T21:56:35Z")

</div>

quoth the Esteban Manchado Velázquez:

> Hi Darren,

Hi,  
I did get it sorted but I wanted to respond to your comments…

\> \> Some suggestions: \> \> 1) I would calculate the method name dinamically with $outtype, instead \> of having 4 if constructions. Something like: \> \> song.send "wavTo#{$outtype.capitalize}"

Hey, that’s pretty neat. I wondered if there was a way to run the method  
based  
on “variable variables”. This is certainly more elegant.

> ```
> 2) I wouldn't use a global variable anyway. I think it's better sending
> 
> ```
> 
> the out type as a parameter.

I have tried this. I guess I don’t fully understand Ruby namespaces, but  
$outtype gets it’s value from a command line option, and if I don’t  
assign it  
to a global then I get:  
undefined local variable or method `outtype’ for main:Object (NameError)

It is assigned thusly:

opts.each do |opt, arg|  
$outtype = arg if ( opt == ‘–out’ )  
[etc…]  
end

If I assign to a regular variable ‘outtype’ and then pass it to  
dispatchFile():

files.each { |file| dispatchFile(file, outtype) }

I get the undefined variable error, so I guess vars in the do loop are  
private, and I don’t know how to use them outside of the loop if they  
are not  
globals.

> ```
> 3) What is "type", a method? It should probably also be a parameter for
> 
> ```
> 
> dispatchFile, but I don’t know if that’s a function or a method.

‘type’ is a simple variable that holds the type of infile. So if the  
infile is  
an ogg, type will be ‘ogg’. It’s value is actually assigned in  
dispatchFile  
(the method I posted), I just removed a few housekeeping lines to keep  
the  
code I posted short.

> ```
> 4) Wouldn't it be better having dispatchFile as a Convert method?
> 
> ```
> 
> Perhaps with other name, but…

I don’t know if this is feasible. It would certainly be a lot of  
rewriting to  
do it. Convert only accepts 1 file at a time. The way my script works is  
to  
create an array of files from the command line arguments, then feed one  
by  
one to dispatchFile, where the proper Convert methods will be run  
depending  
on the input and output formats. This allows me to just send any file to  
Convert and it will Do The Right Thing.

> ```
> def wavToMp3; puts "wavToMp3"; end
> 
> ```
> 
> case type
> 
> ## dispatchFile(‘foo’) ------------------------------------- \>8
> 
> It printed “oggToWav” and “wavToMp3”. It probably has nothing to do with  
> global variables not evaluating, but I can’t tell without seeing the rest  
> of the code.
> 
> ```
> Regards,
> 
> ```

Thanks a lot for your help,  
-d

---

<div class="post-metadata">

**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [June 10, 2006, 9:56pm UTC](https://www.ruby-forum.com/t/global-not-evaluated-properly-in-if-statement-modifier/63022/5 "2006-06-10T21:56:46Z")

</div>

quoth the Matthew S.:

> I’m not able to generalise this result, my similar code (at bottom)  
> works as it should.
> 
> So, at a guess, I’d suggest that $outtype is not actually “mp3” but  
> is “mp3\n”. #puts is smart enough not to include an extra \n, and if  
> you’re using #print, then the extra line break may not be obvious,  
> since it would look just like the result of #puts. Similarly, "mp3 "  
> wouldn’t display as obviously wrong.

Good guess! You were correct even though the bunk value was coming from  
outside the code I posted. Thanks!

> =\> false  
> case type  
> =\> nil  
> Thanks again,  
> -d

---

<div class="post-metadata">

**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [June 10, 2006, 9:12pm UTC](https://www.ruby-forum.com/t/global-not-evaluated-properly-in-if-statement-modifier/63022/6 "2006-06-10T21:12:17Z")

</div>

Hi Darren,

On Sun, Jun 11, 2006 at 03:13:30AM +0900, darren kirby wrote:

> ```
> song.wavToOgg if $outtype == 'ogg'
> song.wavToMp3 if $outtype == 'mp3'
> song.wavToM4b if $outtype == 'm4b'
> song.wavToFlac if $outtype == 'flac'
> 
> ```
> 
> when ‘mp3’  
> \<etc…\>  
> end  
> end

```
Some suggestions:

1) I would calculate the method name dinamically with $outtype, 

```

instead of  
having 4 if constructions. Something like:

```
song.send "wavTo#{$outtype.capitalize}"

2) I wouldn't use a global variable anyway. I think it's better 

```

sending  
the out type as a parameter.  
3) What is “type”, a method? It should probably also be a parameter  
for  
dispatchFile, but I don’t know if that’s a function or a method.  
4) Wouldn’t it be better having dispatchFile as a Convert method?  
Perhaps  
with other name, but…

> When I run this code the 'if’s are never evaluated. That is, I have printed  
> $outtype, and it has a valid value, but the second method which matches the  
> value never runs. If I comment out the ‘if’ and run the two methods manually  
> it works fine.
> 
> In my tests $outtype’s value is ‘mp3’, so why doesn’t song.wavToMp3 run?  
> What am I missing?

```
I made a quick test and it worked for me, but I don't know the rest 

```

of  
your code. This is the example that worked:

## ------------------------------------- 8\<

class Convert  
def initialize(file); end

```
def oggToWav; puts "oggToWav"; end
def wavToOgg; puts "wavToOgg"; end
def wavToMp3; puts "wavToMp3"; end
def wavToM4b; puts "wavToM4b"; end
def wavToFlac; puts "wavToFlac"; end

```

end

def type; “ogg”; end

$outtype = ‘mp3’

def dispatchFile(file)  
song = Convert.new(file)  
case type  
when ‘ogg’  
song.oggToWav  
song.wavToOgg if $outtype == ‘ogg’  
song.wavToMp3 if $outtype == ‘mp3’  
song.wavToM4b if $outtype == ‘m4b’  
song.wavToFlac if $outtype == ‘flac’  
when ‘mp3’  
puts “mp3 nsbb”  
end  
end

## dispatchFile(‘foo’) ------------------------------------- \>8

It printed “oggToWav” and “wavToMp3”. It probably has nothing to do  
with  
global variables not evaluating, but I can’t tell without seeing the  
rest of  
the code.

```
Regards,
```