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comp.lang.ruby

Re: Private methods and self:

Yuu

2/23/2006 10:25:00 PM

James Byrne wrote:
>
> FOR ruby 1.8.4 (2005-12-24) [i386-linux]:
>
> #--------------------------------------------------------------------------
> def foo1
> self.bar
> end
>
> def foo2
> bar
> end
>
> def bar
> puts "In bar"
> end
>
> private :bar
>
> if __FILE__ == $0
>
> foo2 -> 'In bar'
> foo1 -> 'NoMethodError: private method `bar' called for main:Object'
>
> #--------------------------------------------------------------------------
>
> Why the difference in treatment between the explict self reciever and
> the implict self receiver?

Private methods are not allowed to have an explicit receiver
(using the 'self' there is like going out of the object and
then sending the message). The only exception to this rule
are writer methods (def foo=(); ...; end) because without
the self., foo = x is always interpreted as an assignment
to a local variable.

> Regards,
> Jim


E

--
Posted via http://www.ruby-....
2 Answers

James Byrne

2/23/2006 10:38:00 PM

0

E. Saynatkari wrote:

>
> Private methods are not allowed to have an explicit receiver
> (using the 'self' there is like going out of the object and
> then sending the message). The only exception to this rule
> are writer methods (def foo=(); ...; end) because without
> the self., foo = x is always interpreted as an assignment
> to a local variable.
>
> E

Curious that this restriction does not appear to be mentioned in the
Pickaxe book. It also seems, to me, somewhat counter-intuitive. Is it
purposeful behaviour or an artifact of a stylistic convention?

Regards,
Jim

--
Posted via http://www.ruby-....

Tim Hunter

2/23/2006 11:16:00 PM

0

James Byrne wrote:
> E. Saynatkari wrote:
>
>
>>Private methods are not allowed to have an explicit receiver
>>(using the 'self' there is like going out of the object and
>>then sending the message). The only exception to this rule
>>are writer methods (def foo=(); ...; end) because without
>>the self., foo = x is always interpreted as an assignment
>>to a local variable.
>>
>>E
>
>
> Curious that this restriction does not appear to be mentioned in the
> Pickaxe book. It also seems, to me, somewhat counter-intuitive. Is it
> purposeful behaviour or an artifact of a stylistic convention?
>
> Regards,
> Jim
>

Page 35 in the 2nd Edition: "Private methods cannot be called with an
explicit receiverâ??the receiver is always self. This means that private
methods can be called only in the context of the current object; you
canâ??t invoke another objectâ??s private methods."