From: Rob Biedenharn <Rob@...>
Date: 2009-09-04T00:37:57+09:00
Subject: Re: Data::Dumper for Ruby?

On Sep 3, 2009, at 11:06 AM, James Edward Gray II wrote:
> On Sep 3, 2009, at 10:00 AM, Josef Wolf wrote:
> Hello,
>>
>> I am new to Ruby and am about to start my first application that  
>> exceeds the
>> size of gello.rb ;-)
>>
>> One of the first things I am missing is something like perl's  
>> Data::Dumper
>> module.  This module is able to take a (nested) data structure and  
>> dump it
>> in perl syntax.
>>
>> Anybody knows of a similar thing for ruby?
>
> In Ruby we generally use the standard YAML library for that.  If you  
> don't need the content to be human readable, you could also use  
> Marshal, part of Ruby's core.  Ruby 1.9 also ships with a JSON  
> library, which is available as a gem for Ruby 1.8.
>
> Hope that helps.
>
> James Edward Gray II


You might also be interested in the inspect method. It's what irb uses  
to show the last value, but you can call it yourself to get a string  
representation of standard data structures.

irb> my_hash_of_arrays = { 'fibs' => [ 0, 1, 1, 2, 3, 5, 8, 13 ],  
'primes' => [ 2, 3, 5, 7, 11, 13, 17, 19 ], 'squares' => [ 1, 4, 9,  
16 ] }
=> {"fibs"=>[0, 1, 1, 2, 3, 5, 8, 13], "squares"=>[1, 4, 9, 16],  
"primes"=>[2, 3, 5, 7, 11, 13, 17, 19]}
irb> my_hash_of_arrays.inspect
=> "{\"fibs\"=>[0, 1, 1, 2, 3, 5, 8, 13], \"squares\"=>[1, 4, 9, 16],  
\"primes\"=>[2, 3, 5, 7, 11, 13, 17, 19]}"
irb> puts my_hash_of_arrays.inspect
{"fibs"=>[0, 1, 1, 2, 3, 5, 8, 13], "squares"=>[1, 4, 9, 16],  
"primes"=>[2, 3, 5, 7, 11, 13, 17, 19]}
=> nil
irb> p my_hash_of_arrays
{"fibs"=>[0, 1, 1, 2, 3, 5, 8, 13], "squares"=>[1, 4, 9, 16],  
"primes"=>[2, 3, 5, 7, 11, 13, 17, 19]}
=> nil

You can also require the pretty print library.

irb> require 'pp'
=> true
irb> pp my_hash_of_arrays
{"fibs"=>[0, 1, 1, 2, 3, 5, 8, 13],
  "squares"=>[1, 4, 9, 16],
  "primes"=>[2, 3, 5, 7, 11, 13, 17, 19]}
=> nil

And you can get that value into your own string with the PP::pp method  
(and a StringIO to collect the "output")

irb> require 'stringio'
=> true
irb> my_string = StringIO.new
=> #<StringIO:0x394234>
irb> PP::pp(my_hash_of_arrays, my_string)
=> #<StringIO:0x394234>
irb> my_string.rewind
=> 0
irb> my_string.read
=> "{\"fibs\"=>[0, 1, 1, 2, 3, 5, 8, 13],\n \"squares\"=>[1, 4, 9, 16], 
\n \"primes\"=>[2, 3, 5, 7, 11, 13, 17, 19]}\n"
irb> my_string.rewind
=> 0
irb> puts my_string.read
{"fibs"=>[0, 1, 1, 2, 3, 5, 8, 13],
  "squares"=>[1, 4, 9, 16],
  "primes"=>[2, 3, 5, 7, 11, 13, 17, 19]}
=> nil

And all of this is part of Ruby's standard library.

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com