scope_dbl_deny.rb

# scope_dbl_deny.rb

=begin
This code comes from a discussion in rails-br group.

http://groups.google.com/group/rails-br/browse_thread/thread/775784b8e759721f?hl=pt-BR

It is all about two newbie questions:

One about scope operator "::".
And other about double deny "!!".

There is something about metaprogramming in the thread also.

=end

puts '== scope operator =='

module Foo
  def self.do_something
     ::Bar.hi
  end
   module Bar
     def self.hi
      puts "not here..."
     end
  end
end

module Bar
  def self.hi
    puts "I'm here!!!"
  end
end

Foo.do_something

puts '======='

class Test
  def ola
    puts "Hello!!"
  end
end

t = Test.new
t::ola 

puts '======='

module Foo
 def self.do_something
    ::Bar.hi
 end
   module Bar
    def self.hi
      puts "not here..."
    end
  end
end

module Bar
 def self.hi
   puts "I'm here!!!"
 end
 def self.sleep
   puts "zzZZZZ"
 end
end

Foo.do_something # to aqui!!
Foo::Bar.hi   # aqui nao..

# Foo::Bar.sleep # <<<< undefined method

puts '======='

module Foo
  def self.test
    puts 'Foo message'
  end
end

module Bar
  module Foo
    def self.test
      puts 'Bar::Foo message'
    end
  end
  def self.internal_test
    Foo.test
  end
  def self.external_test
    ::Foo.test
  end
end

Bar.internal_test
Bar.external_test

puts ''
puts '== double deny =='

def is_it_true?
  true
end

puts is_it_true?
puts !is_it_true?
puts !!is_it_true?

puts '======='

# When it doesn't make any sense, William Molinari comes to help

def is_it_true?
  nil
end

puts is_it_true?
puts !is_it_true?
puts !!is_it_true?

puts '======='

module Guitar
end

module Blues
   module Sax
   end

   def self.has_guitar?; !!defined? Guitar; end
   def self.has_sax?;    !!defined? Sax;    end
end

module Metal
   def self.has_guitar?; !!defined? Guitar; end
   def self.has_sax?;    !!defined? Sax;    end
end

puts Blues.has_guitar?     # => true
puts Blues.has_sax?        # => true
puts Metal.has_guitar?    # => true
puts Metal.has_sax?       # => false