From: 7stud -- <bbxx789_05ss@...>
Date: 2008-01-24T11:18:01+09:00
Subject: Re: Reusing chunks of code

John Maclean wrote:
> Hi guys,
> 
> I wanted to avoid using the word "block" as it's such a key word in 
> Ruby.
> I'm performing the same test twice here and there must be a way to
> reuse it...
> =begin
> Mon Jan 21 12:51:19 GMT 2008
> simple plays with dirs
> =end
> 
> # create a "singleton object"
> testobj = Object.new
> 
> # play with the object - just a start ;-)
> def testobj.homePlay
>   startDir = Dir.pwd
>   p "current dir is #{startDir}"
>   puts "Dir.getwd == Dir.pwd" if Dir.getwd == Dir.pwd
> 
> # check for ~/
>   if Dir.exist?("#{ENV["HOME"]}")
>     p "changing to ~/"
>   else
>     p "cannot find your home dir. STOP!"
>     exit
>   end
> 
>   Dir.chdir
> 
> # have we changed directory from where we started?
>   if Dir.pwd == startDir
>     p "current dir is still #{startDir}. pwd not changed ;-)"
>   else
>     p "pwd has changed to Dir.pwd"
>   end
> 
>   print "file listing of your home dir...\n\n"
> 
>   p Dir.entries(".").sort # << this an array
>   print "\n\nlisting ../ \n\n"
>   Dir.foreach("..") {|x| p x}
> 
> end
> # end of method testobj.dirPlay
> 
> def testobj.procPlay
>   px = "/proc/"
>   if Dir.exist?("#{px}")
>     p "#{px} dir found - continue"
>   else
>     p "#{px} not found - STOP!"
>     exit
>   end
> end
> 
> # send message to object
> testobj.homePlay
> testobj.procPlay
> 
> __END__
> The question is how to reuse the "testing if directory exists chunk of 
> code"? I'm still thinking procedurally I guess.
> Regards,
> 
> John Maclean
> MSc (DIC)
> +44 7739 171 531


>   puts "Dir.getwd == Dir.pwd" if Dir.getwd == Dir.pwd

According to my book, getwd() and pwd() are the same method.

>   if Dir.exist?("#{ENV["HOME"]}")

Dir.exist?   I don't have that method.  Is it new?


> The question is how to reuse the "testing if directory exists chunk of 
> code"? I'm still thinking procedurally I guess.

Do you mean this part:

>   if Dir.exist?("#{ENV["HOME"]}")
>     p "changing to ~/"
>   else
>     p "cannot find your home dir. STOP!"
>     exit
>   end

You could write:

def check_dir(some_str)
  if Dir.exist?(some_str)
      p "changing to ~/"
    else
      p "cannot find your home dir. STOP!"
      exit
  end
end


but that isn't very general since you hardcoded the message to output. 
You could pass two messages in as arguments, but really what does the 
output message have to do with checking whether the dir exists?  So that 
leaves you with something like this:

def check_dir(some_str)
  return Dir.exist?(some_str)
end


And you could write:

if check_dir("some dir")
    puts 'yep'
else
    puts 'nope'
end

But that code just wraps a definition around a ruby method, so why not 
just call the method directly--like you did in the first place:

if Dir.exist?("some dir")
   puts 'yep'
else
   puts 'nope'
end
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