def behaviour

def.rb

# In Ruby you can use def anywhere in your code, but its behavior
# depends on the context in which it is used.

# Outside a class definition def creates singleton methods

foo = Object.new

# This will create a singleton method in FOO
def foo.speak
  puts "foo"
end


foo.instance_eval do
  def scream
    puts "FOOOO!"
  end
end

puts "Foo singleton methods: #{foo.singleton_methods.join(", ")}"

foo.speak
foo.scream


# Inside a class definition, def creates instance methods

class Bar
  def speak
    puts "bar"
  end

  def define_scream
    def scream
      puts "BAAAAAR!"
    end
  end

  # Except in these cases
  def self.whisper
    puts "sssshhhh bar"
  end

  class << self
    def shut_up
      puts "..."
    end
  end
end

bar = Bar.new
bar.define_scream

puts "Bar singleton methods: #{Bar.singleton_methods.join(", ")}"
puts "Bar instance methods: #{Bar.instance_methods.grep(/speak|scream/).join(", ")}"

bar.speak
bar.scream

Bar.whisper
Bar.shut_up