understand this code..

[Ramesh Jos]

Hi,

While i was going through this code, I couldn't understand what these pieces of code are going to do ... Can anyone help me understand it ??

#!/usr/bin/perl 
 
package Person;
 
sub new
{
    my $class = shift;
    my $self = {
        _firstName => shift,
        _lastName  => shift,
        _ssn       => shift,
    };
    # Print all the values just for clarification.
    print "First Name is $self->{_firstName}\n";
    print "Last Name is $self->{_lastName}\n";
    print "SSN is $self->{_ssn}\n";
    bless $self, $class;
    return $self;
}
sub setFirstName {
    my ( $self, $firstName ) = @_;
    $self->{_firstName} = $firstName if defined($firstName);
    return $self->{_firstName};
}
 
sub getFirstName {
    my( $self ) = @_;
    return $self->{_firstName};
}
1;
 
 

I didn't understand why the following codes are there in defined functions... what is it trying to do ?

my ( $self, $firstName ) = @_;
 

and

 my( $self ) = @_;
 

[numberwhun]

To find out what the @_ is, you are going to want to read the documentation on Special Variables up on Perldoc.

[miller]

You're working with a class definition, so all methods accept the object reference as their first parameter.

Just read perldoc perltoot for a introductory tutorial on object oriented programming in perl.

- Miller

[rovf]

The parameter array @_ is an *alias* for the actual parameter list, which means that if you would assign to some element of @_, and the corresponding parameter is an lvalue, this lvalue would be changed.

Except in the rare cases where you want this to happen, good practice is to assign the parameters to local variables, which also has the advantage of having "understandable" names ($self is easier to understand than $_[0]).