In code I'm working on at present I have two classes of interest. One class is intended for creating a single instance from that manages the database connection. The second class is the base class for a bundle of classes that mediate access to different tables in the database.

The table accessors don't require a connection at create time and can do a limited range of stuff without a connection being provided, but they die if you try to use them in a way that would require a connection and you've not provided one yet. That allows a Task object to be created for example with a bunch of task information, then handed over to a scheduler that gets the task queued (added to the task table).

The table object base class provides members to insert a derived instance into its table and to update/fetch/delete entries matching various criteria. The base class will also create the table for a derived class if the table doesn't exist (the derived class provides a column spec). Typical derived class code looks like:

package Job;

require Exporter;
our @ISA = ('DBObject');
our @EXPORT = qw( );


my $jobTableDef = ['jobs', # Job specifications
     'id INTEGER PRIMARY KEY NOT NULL,
     command VARCHAR(1024) NOT NULL,
     maxrunmins INTEGER,
     numruns INTEGER,
     runtimetotal INTEGER,
     flags VCHAR(20)
     '
    ];

sub new {
    my ($class, %params) = @_;

    $params{flags} = '' unless exists $params{flags};
    return DBObject::new ($class, %params, tableDef => $jobTableDef);
}

1;

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and typical usage looks like:

sub CheckTasks {
    my $self = shift;
    my $task = Task->new (dbh => $self->{db});
    my @readyTasks = $task->getOldest ();
    
    if (@readyTasks) {
        my $taskInfo = $task->fetch (id => $readyTasks[0][0]);
        my $job = Job->new (dbh => $self->{db});
        my $jobInfo = $job->fetch (id => $taskInfo->{jobid});

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DWIM is Perl's answer to Gödel

In reply to Re: How to share DBI connections between objects? by GrandFather
in thread How to share DBI connections between objects? by blahblah

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