# Class doesn't know about calling program's libraries?

**URL:** <https://www.ruby-forum.com/t/class-doesnt-know-about-calling-programs-libraries/158300>\
**Category:** Ruby\
**Created:** [January 21, 2009, 8:48pm UTC](https://www.ruby-forum.com/t/class-doesnt-know-about-calling-programs-libraries/158300 "2009-01-21T20:48:18Z")\
**Posts on this page:** 8\
**Page:** 1

<div class="post-metadata">

**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\
**Post date:** [January 21, 2009, 8:48pm UTC](https://www.ruby-forum.com/t/class-doesnt-know-about-calling-programs-libraries/158300/1 "2009-01-21T20:48:18Z")

</div>

I’m still in my first 24 hours of seriously using classes, so am still  
pretty ignorant. I’ve read a lot, but that only goes so far.

I have a main program which loads some libraries, then calls my main  
method, which call a class -

%w(rubygems ruby-debug readline strscan logger fileutils).each{ |lib|  
require lib }  
main

Inside the class is this line -

opt = Readline::readline( ":: " )

which generates this error -  
uninitialized constant SetLogLevel::Readline (NameError)

Two questions:

1. Is my class really so unaware of the calling program’s namespace (I  
rather think yes).
2. If so, what is the best way to make sure the class has access to the  
libraries already loaded in the calling program?

Thanks for any help!

T.

–

```auto
Tom C., MS MA, LMHC - Private practice Psychotherapist
Bellingham, Washington, U.S.A: (360) 920-1226
<< removed_email_address@domain.invalid >> (email)
<< TomCloyd.com >> (website)
<< sleightmind.wordpress.com >> (mental health weblog)

```

---

<div class="post-metadata">

**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\
**Post date:** [January 21, 2009, 10:19pm UTC](https://www.ruby-forum.com/t/class-doesnt-know-about-calling-programs-libraries/158300/2 "2009-01-21T22:19:56Z")

</div>

Tom C. wrote:

> opt = Readline::readline( ":: " )
> 
> which generates this error -

please post the entire code snippet for help

ilan

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**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\
**Post date:** [January 21, 2009, 10:50pm UTC](https://www.ruby-forum.com/t/class-doesnt-know-about-calling-programs-libraries/158300/3 "2009-01-21T22:50:30Z")

</div>

Tom C. wrote:

> Inside the class is this line -
> 
> opt = Readline::readline( ":: " )
> 
> which generates this error -  
> uninitialized constant SetLogLevel::Readline (NameError)

At a guess: you are running this _before_ you have done require  
‘readline’

The easiest solution is to put

```
require 'readline'

```

at the top of this source file. If it has already been required, this  
will do nothing; but if it has not already been required, it will load  
it in.

> Two questions:
> 
> 1. Is my class really so unaware of the calling program’s namespace (I  
> rather think yes).

I am not sure what you mean about this. Constants are searched for in  
your own class, encoding classes/modules, and the top level.

You can say ::Readline instead of Readline if you mean “I must use the  
one defined in the top level”, but this will only make a difference if  
your class has its own Readline as well, in which case a bare ‘Readline’  
will use the one within your class.

> 1. If so, what is the best way to make sure the class has access to the  
> libraries already loaded in the calling program?

require ‘filename\_containing\_library’ at the top of each source file  
which makes use of the class(es) defined in that library.

---

<div class="post-metadata">

**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\
**Post date:** [January 22, 2009, 9:21am UTC](https://www.ruby-forum.com/t/class-doesnt-know-about-calling-programs-libraries/158300/4 "2009-01-22T09:21:09Z")

</div>

And the exact exception, with backtrace?

---

<div class="post-metadata">

**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\
**Post date:** [January 21, 2009, 11:00pm UTC](https://www.ruby-forum.com/t/class-doesnt-know-about-calling-programs-libraries/158300/5 "2009-01-21T23:00:44Z")

</div>

Ilan B. wrote:

> ilan

Sorry - I thought I’d included enough to justify my questions. Here’s a  
full source file, which produces the problem, minus all methods and  
classes not relevant to the immediate problem -

# SetNet.rb

def main

# Set up logging

run\_log = Toggle\_log.new( ‘logfile.txt’ )  
run\_log.open  
@log = run\_log.log  
logging\_now = run\_log.lgg

# […]

end

class Toggle\_log  
attr\_accessor :log, :lgg  
def initialize( logFileName )  
@logFileName = logFileName  
end

def open  
#create log file  
log\_main = File.open( @logFileName, File::WRONLY | File::APPEND )  
@log = Logger.new( log\_main )  
@log.datetime\_format = “%Y-%m-%d %H:%M:%S”  
@lgg = true

```
# set logging level
@log.level = Logger::INFO # I.e., only INFO level and above will be

```

logged  
@log.info( ‘===== START logging’ ) # just a program place indicator  
puts ‘\> logging started, at INFO level’  
end

def close  
@log.info( ‘===== STOP logging’ ) # just a program place indicator  
puts ‘\> logging stopped’  
@log.close  
@lgg = false  
end  
end

class SetLogLevel  
def initialize( log )  
@log = log  
end  
puts “\> logging level options - from most to least grave -”  
puts “\> 5 = FATAL | 4 = ERROR | 3 = WARN | 2 = INFO | 1 - DEBUG | 0 =  
off”  
puts “\> enter choice (x - exit logging level entry)”  
while true  
opt = Readline::readline( “:: " )  
case opt  
when ‘x’ then break # exit  
when ‘5’ then  
@log.warn( ‘logging level changed to FATAL’ )  
@log.level = Logger::FATAL  
puts ‘\> logging level now FATAL’  
break  
when ‘4’ then  
@log.warn( ‘logging level changed to ERROR’ )  
@log.level = Logger::ERROR  
puts ‘\> logging level now ERROR’  
break  
when ‘3’ then  
@log.warn( ‘logging level changed to WARN’ )  
@log.level = Logger::WARN  
puts ‘\> logging level now WARN’  
break  
when ‘2’ then  
@log.warn( ‘logging level changed to INFO’ )  
@log.level = Logger::INFO  
puts ‘\> logging level now INFO’  
break  
when ‘1’ then  
@log.warn( ‘logging level changed to DEBUG’ )  
@log.level = Logger::DEBUG  
puts ‘\> logging level now DEBUG’  
break  
when ‘0’ then  
@log.warn( ‘logging level changed to OFF; logging closed’ )  
@log.close  
puts ‘\> logging stopped’  
break  
else puts “\> '”+opt+”’ - ? [#2]"  
end  
end  
end

%w(rubygems ruby-debug readline strscan logger fileutils).each{ |lib|  
require lib }  
#Debugger.start  
#debugger # call to ruby-debug

main

# end file

–

```auto
Tom C., MS MA, LMHC - Private practice Psychotherapist
Bellingham, Washington, U.S.A: (360) 920-1226
<< removed_email_address@domain.invalid >> (email)
<< TomCloyd.com >> (website)
<< sleightmind.wordpress.com >> (mental health weblog)

```

---

<div class="post-metadata">

**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\
**Post date:** [January 22, 2009, 9:43am UTC](https://www.ruby-forum.com/t/class-doesnt-know-about-calling-programs-libraries/158300/6 "2009-01-22T09:43:45Z")

</div>

P.S. It would be extremely helpful if you could boil this down to a very  
short program which replicates the problem, and then post that program  
in its entirety.

For example, when I write this:

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

# foo.rb

def main  
Foo.new.bar  
end

class Foo  
def bar  
Readline::readline(“\>\>”)  
end  
end

%w(readline).each{ |lib| require lib }  
main  
---- 8\< -----

and type “ruby foo.rb” then it runs perfectly. The question is, what’s  
different between this and what you posted? Does this program run  
correctly for you? If so, I suspect the problem lies somewhere outside  
what you posted.

This whole process is extremely useful:

1. In the act of minimising the problem, you’ll probably find the  
solution yourself.

2. Even if you don’t, then you have made it as easy as possible for  
other people on the list to understand and/or replicate the problem, and  
hence to find the solution.

The question then becomes simply: “The following piece of code raises  
the exception shown. Why?” Since line numbers in the exception will  
match up exactly to the posted code, an experienced coder will likely  
see the problem at once.

Making life easy for other people makes them much more inclined to help  
you (both now and in the future), as does demonstrating that you’ve done  
your own homework. There’s a very good article on this topic at  
[http://www.catb.org/~esr/faqs/smart-questions.html](http://www.catb.org/~esr/faqs/smart-questions.html)

Regards,

Brian.

---

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**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\
**Post date:** [January 22, 2009, 6:02pm UTC](https://www.ruby-forum.com/t/class-doesnt-know-about-calling-programs-libraries/158300/7 "2009-01-22T18:02:52Z")

</div>

Brian C. wrote:

> end
> 
> 1. Even if you don’t, then you have made it as easy as possible for  
> your own homework. There’s a very good article on this topic at  
> [How To Ask Questions The Smart Way](http://www.catb.org/~esr/faqs/smart-questions.html)
> 
> Regards,
> 
> Brian.

Brian, Thanks for your excellent recommendations. Though I did attempt  
to present a succinct code excerpt containing my problem, I can see,  
after reading your comments, that I could certainly have reduced it to  
essentials, and did not. An excellent idea, and that’s how I’ll present  
problems here in the future. Thanks for the correction!

And thanks for the link.

And thanks for answering my original question about classes’ having  
knowledge of libraries loaded in the calling code.

t.

–

```auto
Tom C., MS MA, LMHC - Private practice Psychotherapist
Bellingham, Washington, U.S.A: (360) 920-1226
<< removed_email_address@domain.invalid >> (email)
<< TomCloyd.com >> (website)
<< sleightmind.wordpress.com >> (mental health weblog)

```

---

<div class="post-metadata">

**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\
**Post date:** [January 22, 2009, 11:11am UTC](https://www.ruby-forum.com/t/class-doesnt-know-about-calling-programs-libraries/158300/8 "2009-01-22T11:11:38Z")

</div>

Brian C. wrote:

> If so, I suspect the problem lies somewhere outside  
> what you posted.

Looking again, I see it now. This boils down what you wrote and  
replicates the problem:

---- 8\< ----  
def main  
Foo.new.bar  
end

class Foo  
def initialize  
puts “Not reached”  
end  
Readline::readline("\>\>")  
end

require ‘readline’  
main  
---- 8\< ----

Can you see what’s wrong with this?