Perl Singleton Objects
This is a quick introduction to perl Singleton objects.
A singleton object is an object that is only instantiated
once throughout an application.
Singleton Uses
Singletons can be used for many things. If you only want one
database connection for a particular application, or a limited
number of connections a singleton database class can handle
managing your open connections.
How to implement
The following is an example of how to put together a
database object that opens a database connection and returns
an existing connection to the caller.This allows your userid/password
to be set in a single location as well. You don't have to have every
piece of code that accesses the database use userid/password. Just use the
DBConnector object and then issue your database calls.
package DBconnector;
my $singleton;
sub new {
my $class = shift;
$singleton ||= bless {}, $class;
}
sub connect {
my $self = shift;
if (exists $self->{dbh}) {
$self->{dbh};
} else {
my $connection = "dbi:mysql:host=$self->{host} \
dbname=$self->{name}";
$self->{dbh} = DBI->connect($connection, \
$self->{user},$self->{password});
}
}
Summary
There are many ways to use singletons. This is just a basic example, but
provides what is needed to create a singleton object.
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