Data::Dumper for Ruby?

[Josef Wolf]

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:umper
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?

 

[Gregory Brown]

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:umpe= r
module. =A0This module is able to take a (nested) data structure and dump= it
in perl syntax.

Anybody knows of a similar thing for ruby?

Do you actually need the syntax preserved, or are you just trying to
serialize data?
If the latter, use Marshal or the YAML std library, or consider JSON
(standard in 1.9, a gem in 1.8)

-greg

 

[James Edward Gray II]

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:umper
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

 

[Rob Biedenharn]

On Sep 3, 2009, at 10:00 AM, Josef Wolf wrote:
Hello,

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:p method
(and a StringIO to collect the "output")

irb> require 'stringio'
=> true
irb> my_string = StringIO.new
=> #<StringIO:0x394234>
irb> PP:p(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
(e-mail address removed)

 

[Josef Wolf]

Thanks for the fast answers!

Do you actually need the syntax preserved, or are you just trying to
serialize data?

The purpose is to check whether the data structures I have built (or am about
to build) are how they should be. So the important thing here is that it is
easy to grasp visually.

If the latter, use Marshal or the YAML std library, or consider JSON
(standard in 1.9, a gem in 1.8)

I know YAML, and I actually use it a lot for configuration or persistent
storage. But I find YAML somewhat hard to read and understand when the data
structures start getting complicated. With output from Data:umper, you
fire up emacs to easily find matching scopes.

 

[Gregory Brown]

Thanks for the fast answers!


The purpose is to check whether the data structures I have built (or am a= bout
to build) are how they should be. =A0So the important thing here is that = it is
easy to grasp visually.

try

require "pp"

pp my_obj

 

[Joel VanderWerf]

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:umper
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?

http://raa.ruby-lang.org/project/amarshal/

It's a bit old, but it does output ruby syntax.

 

[Josef Wolf]

[ ... ]

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

Yeah, this looks very fine. Thanks!

 

[Mark Thomas]

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:umper
module.  This module is able to take a (nested) data structure and dumpit
in perl syntax.

Anybody knows of a similar thing for ruby?

An ex-perl hacker, I used to use Data:umper all the time. Now in
ruby, I find that I don't need the equivalent. I tend to think in
terms of classes and attributes instead of nested data structures. I
can poke around in my class structure in irb.

I think you'll eventually realize that in Perl, there is a tendency to
overuse data structures because it is the most convenient way of
storing data. In ruby there are better ways. This reminds me of an old
post of mine: http://markthomas.org/2008/02/16/language-comparisons-are-always-flawed/
which, although not about Perl per se, covers the same issue.