From: Krzysieq <krzysieq@...>
Date: 2008-03-22T00:02:50+09:00
Subject: Re: Newbie question : private / public methods

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Then it enforces habits, which I've been encouraged to develop anyways - my
managers always told me not to use this.doSomething whenever there is no
risk of ambiguity. Don't You think however, that this is quite harsh - I
mean, don't You think this might get someone into bigger trouble sometime? I
don't know Ruby well enough to think of an example yet, but something tells
me this "feature" could be tricky...

Mateusz: You changed the name of the test class, that's why the error.

Cheers,
Chris

2008/3/21, Stefano Crocco <stefano.crocco@alice.it>:
>
> On Friday 21 March 2008, krzysieq Gazeta.pl wrote:
> > Hi,
> >
> > I'm new both to this mailing list and to Ruby. Here's an example,
> question
> > will come later.
> >
> > >> private.rb
> >
> > class PrivateMethodTest
> >     private
> >     def privateMethod(the_string)
> >         'haha! ' + the_string
> >     end
> >
> >     public
> >     def publicMethod(the_string)
> >         self.privateMethod(the_string)
> >     end
> > end
> >
> > >> private_test.rb
> >
> > require 'private.rb'
> > require 'test/unit'
> >
> > class PrivateMethodTestTest < Test::Unit::TestCase
> >
> >     def test_publicMethod
> >         var = PrivateMethodTest.new()
> >         assert_equal('haha! test', var.publicMethod('test'))
> >     end
> > end
> >
> > Now the question: why is it, that when the self. (bolded in the code) is
> > there, the test fails, whereas if I remove it, the test is successful?
> This
> > is the failure message:
> >
> >   1) Error:
> > test_publicMethod(PrivateMethodTestTest):
> > NoMethodError: private method `privateMethod' called for
> > #<PrivateMethodTest:0x2b0876d805a0>
> >     ./private.rb:9:in `publicMethod'
> >     private_test.rb:8:in `test_publicMethod'
> >
> > What am I missing?
> >
> > Thanks for any help and sorry if this question is silly :)
> > Cheers,
> > Chris
>
>
> Ruby implements private methods as methods which can't be called using an
> explicit receiver (i.e, using the form obj.method_name), but only using
> the
> implicit receiver (that is, method_name). Since the implicit receiver is
> always self, this ensures that private instance methods can only be called
> by
> instance methods of that class (or of derived classes) and can't be
> accessed
> by other instances of the same class. An unpleasant side effect of this is
> that you can't call private methods using the explicit receiver even when
> that
> receiver is equal to the implicit one (that is, self),  which is the
> situation
> you discovered.
>
>

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