Re: How to share DBI connections between objects?

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;
[download]

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});
[download]

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Re^2: How to share DBI connections between objects? by izut (Chaplain) on Mar 26, 2007 at 22:22 UTC
Hi GrandFather, I see you are not using the 'usual' way of doing classes. Usually, I use something like this: `package Job; use base 'DBObject'; sub new { my ($class, %params) = @_; ... return $class->SUPER::new(...); }` [download] There's any special reason for not doing this way? Igor 'izut' Sutton your code, your rules.	[reply] [d/l]
Re^3: How to share DBI connections between objects? by GrandFather (Saint) on Mar 26, 2007 at 22:39 UTC
Ignorance mostly! :) Thanks for the pointer. I'm into my second year of writing Perl and until recently my use of OO has been pretty light. However most things seem to just work so I've only skimmed OO docs to solve immediate issues and have likely missed chunks of the big picture. I'll go back and do some of the required reading real soon now - promise. DWIM is Perl's answer to Gödel	[reply]


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