Forum: Ruby How differs `Private` methods from `singleton methods`?

Can anyone help me to understand the difference between `private
methods` and `singleton methods` in Ruby?

everything because they dont have common stuff:

private methods are not needed to be singleton
and singleton methods are not needed to be private

you can define private singleton methods


you should look at wikipedia first what is the difference between 
"public, protected and private" methods and what are singleton methods 
...

you mix two totally different things together
(its like to compare the color of object A with the size of object B, it 
does not make sense)

Am 02.03.2013 14:09, schrieb Kumar R.:
> Can anyone help me to understand the difference between `private
> methods` and `singleton methods` in Ruby?

Your question doesn't even make any sense.

Stop that.

Private methods are methods defined in a class that only instances of 
that
class can see and use.

Singleton methods are methods added on to an individual instance that
other instances of the same class will not have. Only THAT instance will
have that method. (You can even define a singleton on a class, but the
*instances* of that class won't have the singleton method added. It
applies to that class (which if you know ruby you know a class is also 
an
object in its own right) object only.

unknown wrote in post #1099843:
> Am 02.03.2013 14:09, schrieb Kumar R.:
>> Can anyone help me to understand the difference between `private
>> methods` and `singleton methods` in Ruby?
>
> Your question doesn't even make any sense.
>
> Stop that.

You are carrying wrong perceptions on me, that causes you to keep away 
to understand the core of my question has.

Obviously it is not my problem.

But here I found one such valuable information from the BLACK's book, 
after a long search :

Private and singleton are different
It’s important to note the difference between a private method and a 
singleton method.
A singleton method is “private” in the loose, informal sense that it 
belongs to
only one object, but it isn’t private in the technical sense. (You can 
make a singleton
method private, but by default it isn’t.) A private, non-singleton 
instance method, on
the other hand, may be shared by any number of objects but can only be 
called under
the right circumstances. What determines whether you can call a private 
method isn’t
the object you’re sending the message to, but which object is self at 
the time you
send the message.


Enjoy! :)

D. Deryl Downey wrote in post #1099844:
> Private methods are methods defined in a class that only instances of
> that
> class can see and use.
>
(which if you know ruby you know a class is also an object in its own 
right)

Really I don't know Ruby at all. But trying to learn it and I will do 
definitely.

You guys know it and that's why ir-respecting me continuously. Still I 
will take that blow,as I DON'T know Ruby.


Lastly Thanks for sharing your knowledge, after giving too much curse to 
me.

On Sat, Mar 2, 2013 at 10:09 AM, D. Deryl Downey <me@daviddwdowney.com> 
wrote:
> Private methods are methods defined in a class that only instances of that
> class can see and use.

Not true in Ruby. In Ruby, a private method can only be called on
self. And an explicit receiver (even if it is `self`) is not allowed,
*unless* the method is a setter. E.g.:

1.9.3p194 :001 > class Foo
1.9.3p194 :002?>   attr_accessor :bar
1.9.3p194 :003?>   private :bar=
1.9.3p194 :004?>
1.9.3p194 :005 >   def set_bar_private(obj)
1.9.3p194 :006?>     self.bar = obj
1.9.3p194 :007?>   end
1.9.3p194 :008?>   private :set_bar_private
1.9.3p194 :009?>
1.9.3p194 :010 >   def set_bar_public_using_accessor(obj)
1.9.3p194 :011?>     self.bar = obj
1.9.3p194 :012?>   end
1.9.3p194 :013?>
1.9.3p194 :014 >   def 
set_bar_public_using_private_without_receiver(obj)
1.9.3p194 :015?>     set_bar_private(obj)
1.9.3p194 :016?>   end
1.9.3p194 :017?>
1.9.3p194 :018 >   def 
set_bar_public_using_private_with_self_as_receiver(obj)
1.9.3p194 :019?>     self.set_bar_private(obj)
1.9.3p194 :020?>   end
1.9.3p194 :021?> end
 => nil
1.9.3p194 :022 > f = Foo.new
 => #<Foo:0x94f4d0>
1.9.3p194 :023 > f.bar = 42
NoMethodError: private method `bar=' called for #<Foo:0x94f4d0>
  from (irb):23
  from /Users/eric/.rvm/rubies/ruby-1.9.3-p194/bin/irb:16:in `<main>'
1.9.3p194 :024 > f.set_bar_private 42
NoMethodError: private method `set_bar_private' called for 
#<Foo:0x94f4d0>
  from (irb):24
  from /Users/eric/.rvm/rubies/ruby-1.9.3-p194/bin/irb:16:in `<main>'
1.9.3p194 :025 > f.set_bar_public_using_accessor 42
 => 42
1.9.3p194 :026 > f.bar
 => 42
1.9.3p194 :027 > f.set_bar_public_using_private_without_receiver 43
 => 43
1.9.3p194 :028 > f.bar
 => 43
1.9.3p194 :029 > f.set_bar_public_using_private_with_self_as_receiver 44
NoMethodError: private method `set_bar_private' called for
#<Foo:0x94f4d0 @bar=43>
  from (irb):19:in `set_bar_public_using_private_with_self_as_receiver'
  from (irb):29
  from /Users/eric/.rvm/rubies/ruby-1.9.3-p194/bin/irb:16:in `<main>'
1.9.3p194 :030 >

@Eric ~~ Thank you very much to you.