Pipeline(3) User Contributed Perl Documentation Pipeline(3)NAMEPipeline - Generic pipeline interface
SYNOPSIS
use Pipeline;
my $pipeline = Pipeline->new();
$pipeline->add_segment( @segments );
$pipeline->dispatch();
DESCRIPTION
"Pipelines" are a mechanism to process data. They are designed to be
plugged together to make fairly complex operations act in a fairly
straightforward manner, cleanly, and simply.
USING THE PIPELINE MODULE
The usage of the generic pipeline module is fairly simple. You
instantiate a Pipeline object by using the new() constructor.
Segments can be added to the pipeline with the add_segment method.
The store that the Pipeline will use can be set by calling the store()
method later on. If a store is not set by the time a pipeline is
executing then it will use a store of the type
"Pipeline::Store::Simple".
To start the pipeline running call the dispatch() method on your
Pipeline object.
If a segment returns a Pipeline::Production object then the pipeline
will be terminated early and the production will be returned to the
user. Regardless of when the pipeline is terminated the pipeline's
cleanup pipeline is executed. Segments can be added to the cleanup
pipeline either explicitly by calling the cleanups method to get the
cleanup pipeline and then adding the segment, or implicitly by
returning a segment object from a segment.
To see what is being dispatched within a pipeline dispatch set the
pipeline's debug_all value to true.
INHERITANCE
Pipelines are designed to be inherited from. The inheritance tree is
somewhat warped and should look a little like this:
MySegment --> Pipeline::Segment <--- Pipeline
In other words, everything is a pipeline segment.
METHODS
The Pipeline class inherits from the "Pipeline::Segment" class and
therefore also has any additional methods that its superclass may have.
init( @_ )
Things to do at construction time. If you do override this, it
will often be fairly important that you call and check the value of
$self->SUPER::init(@_) to make sure that the setup is done
correctly. Returns itself on success, undef on failure. The
constructor will fail if you return a false value.
add_segment( LIST )
Adds a segment or segments to the pipeline. Returns itself.
get_segment( INTEGER )
Returns the segment located at the index specified by INTEGER
del_segment( INTEGER )
Deletes and returns the segment located at the index specified by
INTEGER
process_results( ARRAYREF )
Examines each result of a segment and calls process_indv_result
with each element of ARRAYREF. In the case that
process_indv_result returns a production then it is returned to the
caller.
process_indv_result( SCALAR )
Examines a single result and does the appripriate thing with it
(ie, if it is an object it puts it into the store, if it is a
production it returns it to the caller, and if it is a simple value
it gets thrown away. In the case that a value is returned from
process_indv_result the pipeline should terminate.
dispatch()
Starts the pipeline execution. It calls process_results on
anything that a segment returns. The pipeline always returns the
production or true.
dispatch_loop( Pipeline, [ ARRAYREF ] )
The "dispatch_loop" method performs the processing for the pipeline
start_dispatch
Prepares all elements of the pipeline to begin processing a
segment.
end_dispatch
Cleans up all elements of the pipeline after processing a segment.
dispatch_segment( Pipeline::Segment )
The "dispatch_segment" method handles the execution of an
individual segment object.
dispatcher( [Pipeline::Dispatch] )
The "dispatcher" method gets and sets the pipeline dispatcher
object that will be used to traverse the pipeline.
cleanups()
Returns the cleanup pipeline. This is a pipeline in and of itself,
and all the methods you can call on a pipeline can also be called
on this.
cleanup()
Calls the dispatch method on the cleanup pipeline.
segments( [ value ] )
"segments" gets and sets the value of the pipeline list. At
initialization this is set to an array reference.
debug_all( value )
Sets debug( value ) recursively for each segment in this pipeline.
SEE ALSO
"Pipeline::Segment", "Pipeline::Store", "Pipeline::Store::Simple"
"Pipeline::Production", "Pipeline::Dispatch"
AUTHORS
James A. Duncan <jduncan@fotango.com>
Leon Brocard <acme@astray.com>
COPYRIGHT
Copyright 2003 Fotango Ltd. Licensed under the same terms as Perl
itself.
perl v5.14.1 2004-08-09 Pipeline(3)
