why does a ruby method have itself as method

Question

def moo
   puts "moo"
end

moo.moo.moo.moo

this gives

moo
moo
moo
moo

just an oddity, I was curious if this was done on purpose and served some purpose...

Answer 1

I'm guessing you're doing that in console, so you're actually defining the method on the Object, which then defines the method on all the children of Object... which is everything. So your method:

def moo
  puts "moo"
end

Returns nil, and because you defined the method on Object, NilClass has the method as well, so you can call moo on NilClass.

If you do:

class Foo
  def bar
    1 + 1
  end
end

And then:

f = Foo.new
f.bar.bar

You get:

NoMethodError: undefined method `bar' for 2:Fixnum

Answer 2

Perhaps you're defining something on the Object class. Because everything in Ruby is an Object and every method returns something (defaulting to nil), you can call that method on its own result. The moo method returns nil, and so what you are doing is calling moo first on the global object, and then on each nil returned.

You can more explicitly do this:

class Object
  def moo
    puts 'moo'
  end
end

If you generally want to chain methods, you could try this:

class Mooer
  def moo
    puts 'moo'
    self
  end
end

a = Mooer.new
a.moo.moo.moo.moo.inspect