Performing some final housekeeping

When your application has finished processing pipelines, you
need to make sure it takes care of a few cleanup chores. These chores
basically involve releasing the resources you obtained at the beginning
to support pipeline execution.

Garbage collection You should avoid using the DESTROY statement
to clean up resources unless you are sure that the objects you are
destroying are not used elsewhere. PowerBuilder’s garbage
collection mechanism automatically removes unreferenced objects.
For more information, see “Garbage collection and memory
management”.

To clean up when you have finished using pipelines:

1. Destroy the instance that you created of
   your supporting user object.

   To do this, code the DESTROY statement
   in an appropriate script and specify the name of the variable that
   contains that user-object instance.

2. Disconnect from the pipeline’s source
   and destination databases.

   To do this, code two DISCONNECT statements
   in an appropriate script. In one, specify the name of the variable
   that contains your source transaction-object instance.
   In the other, specify the name of the variable that contains your
   destination transaction-object instance.

   Then test the result of each DISCONNECT statement.

3. Destroy your source transaction-object instance
   and your destination transaction-object instance.

   To do this, code two DESTROY statements
   in an appropriate script. In one, specify the name of the variable
   that contains your source transaction-object instance.
   In the other, specify the name of the variable that contains your
   destination transaction-object instance.

For more information on coding the DESTROY and DISCONNECT statements, see
the PowerScript Reference
.

Example

The following code in the Close event of the w_sales_extract window
takes care of these cleanup chores.

Destroying the user-object instance At the beginning of the Close event script, code the following
statement to destroy the instance of the user object u_sales_pipe_logistics (which
is stored in the iuo_pipe_logistics variable):

Disconnecting from the source database Next, code these statements to disconnect from the source
database, test the result of the disconnection, and destroy the
source transaction-object instance (which is stored in the itrans_source variable):

Disconnecting from the destination database Finally, code these statements to disconnect from the destination
database, test the result of the disconnection, and destroy their
destination transaction-object instance (which is stored in the itrans_destination variable):

This part presents a collection of techniques you can
use to implement program access features in the applications you
develop with PowerBuilder. It includes using DDE in an application,
using OLE in an application, building a mail-enabled application,
and adding other processing extensions.

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