From WhyNotWiki

This is mostly for information regarding how to use ruby -- tips and tricks and such -- which is probably what most people are most interested in most of the time. For general information about Ruby, including advocacy and analysis of, see Ruby / About. This article is also my primary repository for snippets and examples at the moment, although I'd like to move them out...

Ruby  edit   (Category  edit) .

[edit] Learning Ruby

http://poignantguide.net/ruby/

http://wiki.rubygarden.org/Ruby/page/show/RubyIdioms RubyIdioms

[edit] Reference

http://www.ruby-doc.org/

http://www.ruby-doc.org/core/

http://www.ruby-doc.org/stdlib/

http://www.rubycentral.com/book/ (Programming Ruby: The Pragmatic Programmer's Guide, First Edition) (buy the Second Edition instead!)

http://www.rubycentral.com/book/lib_standard.html

[edit] Cheat sheet / Quick reference

http://www.zenspider.com/Languages/Ruby/QuickRef.html (very good)

[edit] Miscellaneous / Examples

[edit] Data types: False values

The only false values are nil and false. In particular, 0 and '' are true! (http://woss.name/2006/05/07/notes-from-a-rails-course/)

[edit] Equivalent to Python's if __name__ == "__main__": main ()?

  if $0 == __FILE__
    main
  end

[edit] Examples from Rubyisms in Rails

(Source: Rubyisms in Rails, by Jacob Harris. p. 28-29)

In Java:

Iterator iterator = birdlist.iterator();
while (iterator.hasNext()) {
  Bird bird = (Bird) iterator.next();
  if (bird.endangered()) {
    call_scientists();
    break;
  }
}

In Ruby:

Detection:
call_scientists if birdlist.any? {|bird| bird.endangered? }

Selection:
common_birds = birds.select {|bird, count| count > 5 }
rare_birds = birds.reject {|bird, count| count > 5 }

Accumulation (summing up values):
total_bird_sightings = birds.inject {|total, bird| total += bird.count}

Searching:
winner = contestants.find {|x| x.has_answer? }

Reordering:
titles = jukebox.sort_by {|x| x.title }

Partitioning:
quick, dead = people.partition {|p| p.can_outrun? :bear }
:-) 

Recombination:
blind_dates = restaurants.zip(men, women)
:-)

dates = [:OliveGarden, :TacoBell].zip([:David, :Fred], [:Sara, :Jane])
#     => [[:OliveGarden, :David, :Sara], [:TacoBell, :Fred, :Jane]]

(/Source)

[edit] [Caveats (category)] ENV is not a Hash, like you'd expect, but an Object

It doesn't even have a proper class -- just a singleton class. Its class is "Object".

irb -> ENV.class
    => Object

irb -> puts ENV.class.ancestors
Object
PP::ObjectMixin
Kernel

It does behave like a Hash, however. And it is Enumerable.

{"TERM"=>"linux",
 "SHELL"=>"/bin/bash",
 "LOGNAME"=>"tylerrick",
 "VISUAL"=>"/usr/bin/vim",
 "LINES"=>"55",
 "COLUMNS"=>"155",
 ...}

irb -> ENV.respond_to? :[]
    => true
irb -> ENV.respond_to? :to_a
    => true
irb -> ENV.respond_to? :to_hash
    => true

irb -> puts (class << ENV; self; end).ancestors
Enumerable
Object
PP::ObjectMixin
Kernel

I tried to check if there were any other constants like ENV that were just "Objects", but I didn't find any...

irb -> puts Object.constants.sort.map {|it| it + ': ' + Object.const_get(it).class.to_s }
...

[edit] Types/type conversions/type checking

irb -> nil.to_i
    => 0

"Coercion between types will use to_str, to_int, etc for attempting to coerce an object to a string/integer internally. to_s and to_i produce human-readable representations." (http://woss.name/2006/05/07/notes-from-a-rails-course/)

[edit] Meta-programming: eval

[edit] eval doesn't show the right line numbers!

You have to pass __FILE__ to eval or it will print something useless like (eval):4 in any backtraces, etc.

Grep Houston describes this problem well at http://ghouston.blogspot.com/2006/06/ruby-meta-programming-and-stack-traces.html

His solution/demonstration of his solution:

class Monkey
  module_eval(<<-EOS, __FILE__, __LINE__)
        def see
          puts 'Hello World from Monkey.see'
          puts caller(0)
        end
      EOS
end
    
Monkey.new.see

Hello World from Monkey.see
Monkey-see.rb:5:in `see'
Monkey-see.rb:11

[edit] in the evaled code, __FILE__ will