CODEWITHSUNDEEP
perl
user708537
user708537

Reputation:

What does shift->somesub() do in Perl?

I have been reading this code for a while, and I am not able to figure it out. What does the following do?

sub shared  { shift->state(broadcast => @_) }

https://metacpan.org/source/GRAY/WebService-Google-Reader-0.21/lib/WebService/Google/Reader.pm#L72

Upvotes: 4

Views: 172

Answers (1)

friedo
friedo

Reputation: 66968

In object-oriented Perl, a method's invocant (the thing upon which the method was called, either a class or an instance of a class) is passed into the subroutine as the first parameter.

The parameters to subroutines are found in the special array @_. shift removes the first element of an array and returns it. If you don't specify an explicit argument to shift, it works on @_ by default.

The usual pattern for OO methods is to do stuff like

# foo method
sub foo { 
    my $self = shift;
    # do stuff to $self
    $self->othermethod;
}

What's going on here is they are just using a shortcut to avoid creating the variable $self, and calling the state method on the invocant as returned directly from shift. So your method is equivalent to:

sub shared { 
    my $self = shift;
    $self->state( broadcast => @_ );
}

Upvotes: 13

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