NAME¶
PGObject::Simple - Minimalist stored procedure mapper based on LedgerSMB's
DBObject
VERSION¶
Version 1.8
SYNOPSIS¶
use PGObject::Simple;
my $obj = PGObject::Simple->new(%myhash);
$obj->set_dbh($dbh); # Database connection
To call a stored procedure with enumerated arguments.
my @results = $obj->call_procedure(
funcname => $funcname,
funcschema => $funcname,
args => [$arg1, $arg2, $arg3],
);
You can add something like a running total as well:
my @results = $obj->call_procedure(
funcname => $funcname,
funcschema => $funcname,
args => [$arg1, $arg2, $arg3],
running_funcs => [{agg => 'sum(amount)', alias => 'total'}],
);
To call a stored procedure with named arguments from a hashref. This is
typically done when mapping object properties in to stored procedure
arguments.
my @results = $obj->call_dbmethod(
funcname => $funcname,
funcschema => $funcname,
running_funcs => [{agg => 'sum(amount)', alias => 'total'}],
);
To call a stored procedure with named arguments from a hashref with overrides.
my @results = $obj->call_dbmethod(
funcname => 'customer_save',
funcschema => 'public',
running_funcs => [{agg => 'sum(amount)', alias => 'total'}],
args => { id => undef }, # force to create new!
);
DESCRIPTION¶
PGObject::Simple a top-half object system for PGObject which is simple and
inspired by (and a subset functionally speaking of) the simple stored
procedure object method system of LedgerSMB 1.3. The framework discovers
stored procedure APIs and dispatches to them and can therefore be a base for
application-specific object models and much more.
PGObject::Simple is designed to be light-weight and yet robust glue between your
object model and the RDBMS's stored procedures. It works by looking up the
stored procedure arguments, stripping them of the conventional prefix 'in_',
and mapping what is left to object property names. Properties can be
overridden by passing in a hashrefs in the args named argument. Named
arguments there will be used in place of object properties.
This system is quite flexible, perhaps too much so, and it relies on the
database encapsulating its own logic behind self-documenting stored procedures
using consistent conventions. No function which is expected to be discovered
can be overloaded, and all arguments must be named for their object
properties. For this reason the use of this module fundamentally changes the
contract of the stored procedure from that of a fixed number of arguments in
fixed types contract to one where the name must be unique and the stored
procedures must be coded to the application's interface. This inverts the way
we typically think about stored procedures and makes them much more
application friendly.
SUBROUTINES/METHODS¶
new¶
This constructs a new object. Basically it copies the incoming hash (one level
deep) and then blesses it. If the hash passed in has a dbh member, the dbh is
set to that. This does not set the function prefix, as this is assumed to be
done implicitly by subclasses.
set_dbh($dbh)¶
Sets the database handle (needs DBD::Pg 2.0 or later) to $dbh
_set_funcprefix¶
This sets the default funcprefix for future calls. The funcprefix can still be
overridden by passing in an explicit '' in a call. This is used to
"claim" a certain set of stored procedures in the database for use
by an object.
It is semi-private, intended to be called by subclasses directly, perhaps in
constructors, but not from outside the object.
_set_funcschema¶
This sets the default funcschema for future calls. This is overwridden by
per-call arguments, (PGObject::Util::DBMethod provides for such overrides on a
per-method basis).
_set_registry¶
This sets the registry for future calls. The idea here is that this allows for
application object model wrappers to set which registry they are using, both
for predictability and ensuring that interoperability is possible.
call_dbmethod¶
Does a straight-forward mapping (as described below) to the stored procedure
arguments. Stored procedure arguments are looked up, a leading 'in_' is
stripped off where it exists, and the remaining string mapped back to an
object property. The $args{args} hashref can be used to override arguments by
name. Unknown properties are handled simply by passing a NULL in, so the
stored procedures should be prepared to handle these.
As with call_procedure below, this returns a single hashref when called in a
scalar context, and a list of hashrefs when called in a list context.
call_procedure¶
This is a lightweight wrapper around PGObject->call_procedure which merely
passes the currently attached db connection in. We use the previously set
funcprefix and dbh by default but other values can be passed in to override
the default object's values.
This returns a single hashref when called in a scalar context, and a list of
hashrefs when called in a list context. When called in a scalar context it
simply returns the single first row returned.
WRITING CLASSES WITH PGObject::Simple¶
Unlike PGObject, which is only loosely tied to the functionality in question and
presumes that relevant information will be passed over a functional interface,
PGObject is a specific framework for object-oriented coding in Perl. It can
therefore be used alone or with other modules to provide quite a bit of
functionality.
A PGObject::Simple object is a blessed hashref with no gettors or setters. This
is thus ideal for cases where you are starting and just need some quick
mappings of stored procedures to hashrefs. You reference properties simply
with the $object->{property} syntax. There is very little encapsulation in
objects, and very little abstraction except when it comes to the actual stored
procedure interfaces. In essence, PGObject::Simple generally assumes that the
actual data structure is essentially a public interface between the database
and whatever else is going on with the application.
The general methods can then wrap call_procedure and call_dbmethod calls,
mapping out to stored procedures in the database.
Stored procedures must be written to relatively exacting specifications.
Arguments must be named, with names prefixed optionally with 'in_' (if the
property name starts with 'in_' properly one must also prefix it).
An example of a simple stored procedure might be:
CREATE OR REPLACE FUNCTION customer_get(in_id int) returns customer
RETURNS setof customer language sql as $$
select * from customer where id = $1;
$$;
This stored procedure could then be called with any of:
$obj->call_dbmethod(
funcname => 'customer_get',
); # retrieve the customer with the $obj->{id} id
$obj->call_dbmethod(
funcname => 'customer_get',
args => {id => 3 },
); # retrieve the customer with the id of 3 regardless of $obj->{id}
$obj->call_procedure(
funcname => 'customer_get',
args => [3],
);
AUTHOR¶
Chris Travers, "<chris.travers at gmail.com>"
BUGS¶
Please report any bugs or feature requests to "bug-pgobject-simple at
rt.cpan.org", or through the web interface at
<
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=PGObject-Simple>. I will
be notified, and then you'll automatically be notified of progress on your bug
as I make changes.
SUPPORT¶
You can find documentation for this module with the perldoc command.
perldoc PGObject::Simple
You can also look for information at:
- •
- RT: CPAN's request tracker (report bugs here)
<http://rt.cpan.org/NoAuth/Bugs.html?Dist=PGObject-Simple>
- •
- AnnoCPAN: Annotated CPAN documentation
<http://annocpan.org/dist/PGObject-Simple>
- •
- CPAN Ratings
<http://cpanratings.perl.org/d/PGObject-Simple>
- •
- Search CPAN
<http://search.cpan.org/dist/PGObject-Simple/>
ACKNOWLEDGEMENTS¶
LICENSE AND COPYRIGHT¶
Copyright 2013-2014 Chris Travers.
Redistribution and use in source and compiled forms with or without
modification, are permitted provided that the following conditions are met:
- •
- Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer as the first lines of
this file unmodified.
- •
- Redistributions in compiled form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the source
code, documentation, and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) "AS IS" AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.