The new safe navigation operator in Ruby 2.3

sno.rb

#!/usr/bin/env ruby

################################################################################
#
# Watch out for the unusual argument evaluation rules with the new
# safe navigation operator in Ruby 2.3.
#
# It short circuits just like the logic operators.  This is different
# than how the `try' method works in ActiveSupport.
#
################################################################################
class Test
  def foo; self; end # Always returns `self'
  def bar; nil;  end # Always returns `nil'
  def putsN (n); puts(n.to_s); end
end

################################################################################
# Use the &. operator to guard against nil values:
t = Test.new
x = 1

t&.foo&.putsN(x += 1) # x is now 2
t&.bar&.putsN(x += 1) # x is still 2
t.putsN(x)            # see for yourself

################################################################################
# Works a lot like:
x = 1

(y = t.foo) && y.putsN(x += 1) # x is now 2
(y = t.bar) && y.putsN(x += 1) # x is still 2
t.putsN(x)

################################################################################
# But differently than:
class Object
  def try (name, *args)
    send(name, *args) unless nil?
  end
end

x = 1
t.try(:foo).try(:putsN, x += 1) # x is now 2
t.try(:bar).try(:putsN, x += 1) # x is now 3!
t.putsN(x)