Object private methods

[Paolino]

Hello

I noticed that Object private methods are available everywhere.
This I noticed exploring 'main' instance defining a method

Can I have some explanation on this form of globalizing ?


TIA

Paolino





___________________________________
Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB
http://mail.yahoo.it

 

[Robert Klemme]

Hello

I noticed that Object private methods are available everywhere.
This I noticed exploring 'main' instance defining a method

Can I have some explanation on this form of globalizing ?

Dunno what exactly you are looking for...

Typically these methods reside in Kernel and are defined like this:

module Kernel
private
def foo() "something" end
end

This works since all objects eventually inherit Kernel:

18:45:30 [~]: ruby -e 'p String.ancestors'
[String, Enumerable, Comparable, Object, Kernel]

What else do you want to know?

Kind regards

robert

 

[daz]

Hello

I noticed that Object private methods are available everywhere.
This I noticed exploring 'main' instance defining a method

Can I have some explanation on this form of globalizing ?

It's useful to have some methods available almost anywhere ...

$_ = 'A B C'
puts split # there are two of the private methods
#-> A
#-> B
#-> C

.... but not *everywhere* ...

puts 3.split

#-> ... private method `split' called for 3:Fixnum (NoMethodError)

There is no 'split' method for Fixnum.
Fixnum inherits from Object and a 'split' was found but, fortunately,
a sensible error message was produced before disaster struck.


We can define a (silly) split for Fixnum:

class Fixnum
def split
self / 2.0
end
end

puts 3.split
#-> 1.5

.... and we can make it private:

class Fixnum
private :split
end

puts 3.split
#-> ... private method `split' called for 3:Fixnum (NoMethodError)

.... but from within Fixnum, it's not private:

class Fixnum
def splitter
split # <-----XXXXX
end
end

puts 5.splitter
#-> 2.5

So when we use 'puts' or 'split', or any other of the Kernel methods,
without a dot in front of them ("no receiver"), our homeland is a
place provided for us where all of those methods are non-private.
(A bit like standing to the left of the arrow <-----XXXXX
... right inside an object) <ROCK>

How warm and fluffy do you feel now ?


daz

Chorus: <i>Quit clownin', goof</i>

 

[Robert Klemme]

It's useful to have some methods available almost anywhere ...

$_ = 'A B C'
puts split # there are two of the private methods
#-> A
#-> B
#-> C

... but not *everywhere* ...

puts 3.split

#-> ... private method `split' called for 3:Fixnum (NoMethodError)

There is no 'split' method for Fixnum.

Not exactly: Fixnum inherits split from Kernel and it's just not
accessible with a receiver because it's private:

09:24:18 [Oracle]: ruby -e '$_="a,b,c"; p 1.instance_eval { split(/,/) };
p 1.sendsplit, /,/)'
["a", "b", "c"]
["a", "b", "c"]

Fixnum inherits from Object and a 'split' was found but, fortunately,
a sensible error message was produced before disaster struck.

Well you could argue about the sensibility (?) of the error message.
Privacy is just a means to make it *look* like a global function.

Kind regards

robert

 

[Han Holl]

------=_Part_1355_26015289.1127898653938
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

Also interesting:
irb(main):001:0> self.puts 'aa'
NoMethodError: private method `puts' called for main:Object
from (irb):1
irb(main):002:0> puts 'aa'
aa
=3D> nil
irb(main):003:0>

So the receiver _must_ be an implicit self.

Cheers,

Han Holl

------=_Part_1355_26015289.1127898653938--

 

[Paolino]

Dunno what exactly you are looking for...

Typically these methods reside in Kernel and are defined like this:

module Kernel
private
def foo() "something" end
end

This works since all objects eventually inherit Kernel:

What else do you want to know?

My question was about something different probably.

But why/how private messages are not accepting a receiver ?
Is this their actual definition?

I suppose 'main' does some tricks when I define a method "there".
It pushes it in Object private space.

Am I defining it in its singleton?

Where exactly I find myself in the "global" ?I see self.is_a? Class is
false,so I suppose I'm not in the sigleton space.

Am I inside a method definition () defining a nested method?

Thanks for answers

Paolino





___________________________________
Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB
http://mail.yahoo.it

 

[ts]

P> But why/how private messages are not accepting a receiver ?
P> Is this their actual definition?

yes,

P> I suppose 'main' does some tricks when I define a method "there".

no, not really. ruby has self and *internally* ruby_class which give it
where the method must be defined.

For example :

* at top level it has : self = main, ruby_class = Object

when you define a method at top level this will be an Object method

* in the class A, it has : self = A, ruby_class = A

when you define a method in A, this will be an instance method for A


Guy Decoux

 

[Paolino]

P> But why/how private messages are not accepting a receiver ?
P> Is this their actual definition?

yes,

P> I suppose 'main' does some tricks when I define a method "there".

no, not really. ruby has self and *internally* ruby_class which give it
where the method must be defined.

For example :

* at top level it has : self = main, ruby_class = Object

when you define a method at top level this will be an Object method

* in the class A, it has : self = A, ruby_class = A

when you define a method in A, this will be an instance method for A

This is the first bad hack I meet in the Ruby machine.
Wasn't enough to operate inside a singleton and define a method_added
hook to paste the added method in Object private space?

Anyway thanks a lot for explanations .

Paolino


___________________________________
Yahoo! Messenger: chiamate gratuite in tutto il mondo
http://it.messenger.yahoo.com

 

[ts]

P> Wasn't enough to operate inside a singleton and define a method_added
P> hook to paste the added method in Object private space?

Too complex what you do

and don't forget that main, for ruby, is an object also it need the
distinction between self and ruby_class at least for this case

moulon% cat b.rb
#!/usr/bin/ruby
class A
end

A.class_eval do
p self
def a
puts "A#a"
end
end

A.instance_eval do
p self
def a
puts "A::a"
end
end

A.a
A.new.a

moulon%

moulon% ./b.rb
A
A
A::a
A#a
moulon%


Guy Decoux