Learning Perl Objects, References amp;amp; Modules [Electronic resources] نسخه متنی

9.13 Getters That Double as Setters

Another alternative to the pattern
of creating two different methods for getting and setting a parameter
is to create one method that notes whether or not it gets any
additional arguments. If the arguments are absent,
it's a get operation; if the arguments are present,
it's a set operation. A simple version looks like:

sub color {
my $shift;
if (@_) {              # are there any more parameters?
# yes, it's a setter:
$self->{Color} = shift;
} else {
# no, it's a getter:
$self->{Color};
}
}

Now you can say:

my $tv_horse = Horse->named("Mr. Ed");
$tv_horse->color("black-and-white");
print $tv_horse->name, " is colored ", $tv_horse->color, "\n";

The presence of the parameter in the second line denotes that you are
setting the color, while its absence in the third line indicates a
getter.

While this strategy might at first
seem attractive because of its apparent simplicity, it complicates
the actions of the getter (which will be called frequently). This
strategy also makes it difficult to search through your listings to
find only the setters of a particular parameter, which are often more
important than the getters. In fact, we've been
burned by this in the past when a setter became a getter because
another function returned more parameters than expected after an
upgrade.