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Re: Getting Confused with the '->' operator

by elusion (Curate)
on Sep 30, 2002 at 22:34 UTC ( #201878=note: print w/replies, xml ) Need Help??

in reply to Getting Confused with the '->' operator

The arrow operator always operates on the value to its left. That means that your second example would be equivalent to this:
my $result1 = $Person->name('Homer'); my $result2 = $result1->job('safety inspector'); my $result3 = $result2->wife('Marge'); $result3->fav_food('Duff');
where the result variables are temporary. In order for the code to work as expected, the methods (name, job, wife, fav_food) must return the original object. A sample method that works this way would look like this (assuming the object is a hash ref):
sub name { my ($self, $value) = @_; if (defined $value) { # if a value is given $self->{name} = $value; # set the value return $self; # return the original object } return $self->{name}; # else return the name }
This code fragment will set the value and return the object if a value is given, else it will return what the name is set as.

So why do you sometimes see the original object ($Person in this case) have multiple method calls originating from the original obect on multiple lines? Because if the method returns a value other than itself (which is quite common), it will try to call the method on that value, and most likely fail.

elusion :

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