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9.6. Making a Method Work with Either Classes or Instances
All you need to fix this is a way to detect whether the method is called on a class or an instance. The most straightforward way to find out is with the ref operator. This operator returns a string (the classname) when used on a blessed reference, and undef when used on a string (like a classname). Modify the name method first to notice the change:
sub name {
my $either = shift;
ref $either
? $$either # it's an instance, return name
: "an unnamed $either"; # it's a class, return generic
}Here the ?: operator selects either the dereference or a derived string. Now you can use it with either an instance or a class. Note that you changed the first parameter holder to $either to show that it is intentional:
print Horse->name, "\n"; # prints "an unnamed Horse\n"
my $tv_horse = Horse->named("Mr. Ed");
print $tv_horse->name, "\n"; # prints "Mr Ed.\n"and now you'll fix speak to use this:
sub speak {
my $either = shift;
print $either->name, " goes ", $either->sound, "\n";
}Since sound already worked with either a class or an instance, you're done!
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| 9.5. Inheriting the Constructor |  | 9.7. Adding Parameters to a Method |
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