From: Robert Klemme <bob.news@...>
Date: 2004-01-27T03:14:55+09:00
Subject: Re: Print empty values to a file?


"Qubert" <qubert@orbit.gotdns.com> schrieb im Newsbeitrag
news:ae5c96cb.0401260829.63d13a13@posting.google.com...
> I am in the middle of writing a wrapper to FORTRAN programs using
> Ruby.  It going great so far.  The problem that I need this groups
> help to solve follows:
>
> For the purposes of a reference, a log and to allow continuation of
> the script, I have created a function that writes inquired values to a
> file, as follows:
>
> def savevaribles
>   fs = File.new("./savedvaribles.rb","w")
>   # Saved variables from harmprocessing.rb
>   fs.puts "# Saved variables from harmprocessing.rb"
>   fs.puts "$year = #{$year}"
>   fs.puts "$gonl = #{$gonl}"
>   fs.puts "$tm = #{$tm}"
>   fs.puts "$timezone = #{$timezone}"
>   fs.close
> end

A first remark: you should definitely use the block form:

File.open("savedvaribles.rb", "w") do |fs|
  fs.puts "# Saved variables from harmprocessing.rb"
  # ...
end

This way you ensure the file is closed properly, regardless how you leave
the block.

> Which creates a file that I can "load" with all my variables.
> # Saved variables from harmprocessing.rb
> $gonl = 149.98435
> $tm = 135
> $timezone = -9
>
> The list is much more extensive than this and many of the values are
> not set until later in the analysis.  If the value is not set or if it
> is "nil" the commands #{$value} is blank, which is fine except,
> $value1 =
> $value2 = 42
> Upon reading the file, the value of $value1 is set to 42 also, which
> confuses further analyses.
> So I am trying to figure out a cleaver means to check if each value
> exists or nil then 'puts "nil"' so there are no more blanks.
> I can do this the brute force method, with if/then statements
> everywhere, but I was wondering if there is a Ruby way to accomplish
> this.

If you don't need to edit those variables by hand you can marshal them.  A
convenient way is to use a hash for that

# names must be an array of global variable names like ["$foo", "$bar"]
def save_vars(names)
  h = {}
  # for globals only
  names.each {|name| h[name]=eval name}
  save_hash h
end

def save_hash(hash)
  File.open("savedvaribles.rb", "wb") do |fs|
    Marshal.dump( hash, fs )
  end
end

def load_hash
  File.open("savedvaribles.rb", "rb") do |fs|
    Marshal.load( fs )
  end
end

def load_vars
  load_hash.each do |name, val|
    # note: name contains the name of a global var
    # val is referenced directly!
    eval "#{name} = val"
  end
end

Something along these lines.

    robert