Ruby 1.9 features, tips & tricks you may not know about...

ruby-1.9-tips.rb

def tip(msg); puts; puts msg; puts "-"*100; end

#
# 30 Ruby 1.9 Tips, Tricks & Features:
# http://www.igvita.com/2011/02/03/new-ruby-19-features-tips-tricks/
#

tip "Upgrading to Ruby 1.9 is simple: rvm install 1.9.2 && rvm --default 1.9.2"

tip "Ruby 1.9 supports named captures in regular expressions!"
  p "hello 2011!".match(/(?<year>\d+)/)[:year]  # => "2011"

tip "Ruby 1.9 uses Oniguruma as a new regex engine, and @pragprog has a fantastic (and free!) PDF on it: http://bit.ly/hIzvOi"

tip "Ruby 1.9 allows default arguments at the beginning of a method!"
  def f(a=1, b); p [a,b]; end;
  p f(2) # => [1, 2]

tip "Ruby 1.9 changed #to_s to use Object#inspect by default!"
  puts({a:1, b:[2,3]}.to_s) # => {:a=>1, :b=>[2, 3]}

tip "Ruby 1.9 added Hash#assoc, which returns a two element array [key, hsh[key]]!"
  p({a: 1, b: 2}.assoc(:b)) # => [:b, 2]

tip "Ruby 1.9 allows splat argument anywhere in a method's parameter list"
  def a(a,*b,c); p [a,b,c]; end
  p a(1,2,3,4) # => [1, [2, 3], 4]

tip "Ruby 1.9 allows matching regular expressions against a symbol!"
  p :ruby_symbol.match(/symbol/) # => 5

tip "Ruby 1.9 supports new & more compact hash syntax for symbol keys! "
  p({a:1, b:2}) # => {:a=>1, :b=>2}

tip "Ruby 1.9 supports new 'stabby proc' syntax!"
  f = -> a,b { p [a,b] }
  p f.call(1,2) # => [1, 2]

tip "Ruby 1.9 hashes preserve the insertion order of elements! for the curious: http://bit.ly/e0oEun"
  p({a:1, b:2}) # => {:a=>1, :b=>2}

tip "Ruby 1.9 supports 4 ways to call a proc!"
  f =->n {[:hello, n]}
  p f[:ruby]       # => [:hello, :ruby]
  p f.call(:ruby)  # => [:hello, :ruby]
  p f.(:ruby)      # => [:hello, :ruby]
  p f === :ruby    # => [:hello, :ruby]

tip "Ruby 1.9 no longer supports .each on a string! instead, use: .chars, .bytes, .lines, .each_char, etc..."

tip "Ruby 1.9 allows default parameters in procs & lambdas!"
  f =-> a,b=1,*c { p [a,b,c] }
  p f.call(1)   # => [1, 1, []]
  p f.(1,2)     # => [1, 2, []]
  p f[1,2,3]    # => [1, 2, [3]]

tip "Ruby 1.9 added ObjectSpace.count_objects method which returns a hash of types+counts of objects in current process"

tip "Ruby 1.9 added each_with_object to Enumerable!"
  p (1..10).each_with_object([]) {|i, a| a << i*2 } # => [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]

tip "Ruby 1.9 added Object#public_send, which will raise an error on messages to private methods!"

tip "Ruby 1.9 added Enumerable#sample(n), which returns n random elements!"
  p [1,2,3,4].sample(2)  # => [2, 3]

tip "Ruby 1.9 added Kernel#define_singleton_method"
  c = 'cat'; c.define_singleton_method(:hi) { p 'hi' };
  p c.hi  # => "hi"

tip "Ruby 1.9 added support for block-local variables!"
  v = 'ruby'; [1,9].map {|val; v| v = val }
  p v # => "ruby"

tip "Ruby 1.9 blocks now allow blocks as parameters!"
  b = -> v, &blk { p [v, blk.call] }
  p b.call(:a) { :b } # => [:a, :b]

tip "Ruby 1.9 threads are now mapped (1:1) to OS threads! ex: gdb -p [ruby PID], info threads - yes, there is still a GIL."

tip "Ruby 1.9 added Process.daemon to put current process into background, see docs @ http://bit.ly/hY55HK"

tip "Ruby 1.9 ships with JSON support: require 'json' + Kernel#j, Kernel#jj"
  require 'json'
  h = {a:1,b:2}
  j(h); jj(h)

tip "Ruby 1.9 allows you to set a default input encoding with a magic comment (http://bit.ly/dRhgHy) ex: # encoding: UTF-8"

tip "Ruby 1.9 added GC.count & GC::Profiler (http://bit.ly/fhPsiJ)"
  GC::Profiler.enable; GC.start; puts GC::Profiler.result

tip "Ruby 1.9 allows you to introspect YARV bytecode!"
  puts RubyVM::InstructionSequence.compile('a = 1; p 1 + a').disassemble

tip "Ruby 1.9 shipped with MiniTest, a successor to Test::Unit! worth a look: http://bit.ly/ea2xmP"

tip "Ruby 1.9 regular expressions allow you to invoke subpatterns (recursively, even) with \g<name>! http://bit.ly/ikgT2t"

tip "Ruby 1.9 added Process.spawn which will execute cmd in subshell"
  pid = spawn('echo hello')
  p Process::waitpid2(pid)  # => [62777, #<Process::Status: pid 62777 exit 0>]

tip "Ruby 1.9 added Enumerable.reduce, which is equivalent to Enumerable.inject"
  p [1,2,3].reduce(:+)  # => 6

tip "Ruby 1.9 supports new 'stabby proc' syntax!"

The new ->{} syntax creates lambda Procs, not just regular Procs. There is quite a difference in behavior.

irb(main):001:0> foo =->{}
=> #<Proc:0x270d380@(irb):1 (lambda)>
irb(main):002:0> foo.class
=> Proc
irb(main):003:0> foo.lambda?
=> true