Class variables and how to set them up only once


#1

I’m trying to share a File object with everything that inherits from
Superclass, for logging.

I’m trying to come up with a nice clean way of handling this, and this
isn’t it:
Right now it’s doing a begin/rescue/end to see if the @@logger.nil?
(which throws an error if it doesn’t exist), and setup @@logger in the
rescue.

The other thought I had was to take the setupLogger out of initialize,
have a single dummy instance of SuperPage, and call setupLogger from
that class once. That seems even worse.

I’m sure other people can think of more elegant ways of handling this,
and I’d sure like to hear their suggestions :slight_smile:

I tried putzing around with class_variables, but I couldn’t seem to
get at those from within a class.

–Kyle

class SuperPage
def initialize()
#lots of stuff
setupLogger()#setsup an @@logger member that the log methods use
ObjectSpace.define_finalizer(self,
SuperPage.create_finalizer(@@logger))
end

def logError(message)
log(:Error,message)
throw :assertion_error
end

def log(type,message)
@@logger.puts("#{…ugly long string that includes the message…}")
end

def setupLogger(path=“c:\#{DateTime.now.to_s.gsub(’:’,’-’)}.xml”)
begin
@@logger.nil?
rescue
puts “I’m setting up the logger, you should only see me once”
@@logger=File.new(“c:\#{DateTime.now.to_s.gsub(’:’,’-’)}.xml”,“w”)
@@logger.puts “”
@loggerSetup=true
end
end
end


#2

And after I said I couldn’t find a way of getting at class_variables
from inside the class, the obvious occurred to me, whether or not it’s
the ‘right’ way.
self.class.class_variables


#3

Right, so the way I wrote previously, or this way:

def setupLogger(path=“c:\#{DateTime.now.to_s.gsub(’:’,’-’)}.xml”)
unless self.class.class_variables.include?"@@logger"
puts “I’m setting up the logger, you should only see me once”
@@logger=File.new(“c:\#{DateTime.now.to_s.gsub(’:’,’-’)}.xml”,“w”)
@@logger.puts “”
@loggerSetup=true
end
end


#4

Hi –

On Fri, 27 Jul 2007, Kyle S. wrote:

Right, so the way I wrote previously, or this way:

def setupLogger(path=“c:\#{DateTime.now.to_s.gsub(’:’,’-’)}.xml”)
unless self.class.class_variables.include?"@@logger"
puts “I’m setting up the logger, you should only see me once”
@@logger=File.new(“c:\#{DateTime.now.to_s.gsub(’:’,’-’)}.xml”,“w”)
@@logger.puts “”
@loggerSetup=true
end
end

What about:

@@logger ||= File.new …

David


#5

On 26.07.2007 21:30, Kyle S. wrote:

I’m trying to share a File object with everything that inherits from
Superclass, for logging.

The other thought I had was to take the setupLogger out of initialize,
have a single dummy instance of SuperPage, and call setupLogger from
that class once. That seems even worse.

I’m sure other people can think of more elegant ways of handling this,
and I’d sure like to hear their suggestions :slight_smile:

There is at least one logging package for Ruby (Log4R). I’d use that
one instead of creating my own.

Kind regards

robert


#6

dblack,
I’ve never tried to use ||= before… but damn if that
doesn’t work well! I was expecting it to die like my @@whatever=:this
unless @@whatever had when I tried that. Neat!

Robert,
I’ve found the docs for log4r to be slightly better than
those for well… umm. nothing. There about the worst docs I’ve found
for a widely used package :wink: I’ve used log4r in other projects
several months ago, but didn’t feel like going through the pain of
setting it up and re-learning it. While it’s a good lib, the docs are
horrible.

Thanks,
Kyle