Hi all,
I just work my way through "Learning Perl Objects, References & Modules". Now at one
point, I am stuck: Randal introduces classes and methods in Chapter 8.
He gives the following example for overriding methods:
{ package Mouse
@ISA = qw{Animal};
...
sub speak {
my $class = shift;
...
Animal::speak($class);
...
}
}
Since there is a method speak in Mouse, it would override the parent's classes method
Animal::speak if the latter were not called explicitly.
But, as Randal points out, this forces Perl to look for speak in Animal and nowhere
else - without the method invocation arrow, it cannot check @ISA for ancestor classes.
So far, I get the point. But then he introduces the following solution:
$class->Animal::speak(@_);
Apart from the fact that @_ should be unnecessary here (or did I get something wrong),
this should expand to:
Mouse::Animal::speak("Mouse");
And when Perl does not find Animal::speak in Mouse, to:
Animal::Animal::speak("Mouse";
and to higher classes if speak is not found there. Now my question:
Does Perl reduce Animal::Animal::speak("Mouse") automatically to
Animal::speak("Mouse"). And, if speak is not in Animal, how does it handle an
expression like:
LivingCreature::Animal::speak("Mouse");
It seems to me that the hard-coded package name we got rid of by using method calls
just got back into our syntax. At the same time, I am sure the code works (have not
tried it yet) and Perl does as it should.
But how does this work?
Thanks for any explanations,
Jan
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