in reply to Re: Re: Instance field access from private methods
in thread Instance field access from private methods

Let me know if I'm wrong, but this sure looks like it's inheriting something w/o $self being passed to me.

But it *is* passed, actually $bob is passed as the first element of @_ which is seen in the output

Goodbye C2=HASH(0x177f054) World

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So you would normally shift off the first element to a lexical variable often called $self to use the subroutine as a method in OO-style

sub printGoodBye {
  my $self = shift;
  print "Goodbye ";
  $self->printWorld();
}
sub printWorld{ 
    my $self = shift;
    print "World\n ";
}

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So inheritance is really in play here.
I am also a newbie when it comes to perl-OO, so I watch this thread with keen interest.(++)

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Re: Re: Re: Re: Instance field access from private methods
by markcsmith (Novice) on Oct 23, 2002 at 20:08 UTC

    I think you have shown me what I'm doing wrong here. Inside of your printGoodBye method, you call printWorld() w/ $self as the invocant whereas I had always been calling that method without any invocant at all. Heh, java rears it's ugly head :)

    This must be what robartes meant when he wrote: "...it is a good idea that even your private methods use the class' public accessor methods to get at private instance attributes."

    Excellent, excellent.

    Now, I'm still not too sure about a subroutine being required to recieve a copy of the invocant in order for it to be classified as a method and thus inheritable. You are right that printGoodBye() recieves the invocant, but printWorld() does not (or else there would be a HASH=... after "World" in the output). However, printWorld is still inherited from C1 by C2.

    So, chances are, I'm thinking about this in java-world and being stupid again. But, my original question has been answered, so thanks, guha.



    Mark
[reply]
      The reason printWorld is not printing "HASH=" is that you are calling it incorrectly. You're invoking it as a subroutine, not as a method, so it is not inherited at all; it just happens to be in the same package as printGoodBye.

      The correct way to call it is to use the version of printGoodBye in guha's post, which uses $self->printWorld() instead.

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[d/l]

      Well I think the thing is that you invoke printGoodBye as subroutine with no argument, so in your example nothing should be printed

      If you would for some reason put 

      printGoodBye(@_); # instead

      [download]
      you would see the HASH-stuff

      However I think that in order for inheritance to work, the "hash" or instance or ... needs to be BLESSED to some package

      The reason it *seems* to work is that printWorld and printGoodBye are defined in the same package.

[reply]
[d/l]

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