Understanding Application Computations

Application Computations are units of logic that set the value of a single page or application level item and are run at the same point across multiple pages in an application. Like page level computation, application computations can be based on static values, item values, PL/SQL, or SQL.

Topics:

About Application Computations
Creating an Application Computation
Accessing the Application Computation History Report

About Application Computations

A common use of an application item is to store the value of the last page viewed in the application. By storing the value in an item, you can add a back button and then redirect the user to the page ID captured by the computation. This type of computation works well, for example, when you need to enable users to back out of an error page.

The following is an example of a computation that stores the last page visited. In this example, the computation:

Stores the last application page visited to an item named LAST_PAGE

Checks that the value of a CURRENT_PAGE_ITEM is of type PL/SQL Function Body with a Computation body of:

BEGIN
   :LAST_PAGE := nvl(:CURRENT_PAGE,:APP_PAGE_ID);
   :CURRENT_PAGE := :APP_PAGE_ID;
   RETURN :LAST_PAGE;
END;

About Application Computations that Execute On New Instance

Typically an application computation runs at the same point across multiple pages in an application. The exception is computations having a Computation Point of On New Instance. This type of computation only runs when a user first accesses your application. This type of computation is useful when you need to only retrieve information once within a user's session (for example, to retrieve a user's job title).

Creating an Application Computation

To create an application computation:

Navigate to the Shared Components page:
1. Click Application Builder on the Workspace home page.
2. Select an application.
3. On the Application home page, click Shared Components.
  
  The Shared Components page appears.
Under Logic, select Application Computation.
Click Create.
For Computation Item, select the item this computation will affect.
For Computation Point, select a process point at which this computation should be performed.
For Computation:
1. For Computation - Enter the computation logic that corresponds to the computation type.
2. Computation Error Message - Enter the error message that displays if the computation fails.
From Authorization Scheme (optional), select an authorization scheme which must evaluate to True in order for this computation to execute.
Under Conditions:
1. Condition Type - Select a condition type that must be met in order for this computation to execute.
2. Expression 1 and Expression 2 - Uses these attribute to conditionally control whether or not the computation executes. Enter values in this attribute based on the specific condition type you select. The computation will execute if the specified condition is met.
From Build Option (optional), select a build option for this component.
Click Create.

About the Application Computations Page

Once you create an application computation, it appears on the Application Computations page. You control how the page displays by making a selection from the View list. Available options include:

Icons (the default) displays each computation as a large icon. To edit an computation, click the appropriate icon.
Details displays each application process as a line in a report. To edit a computation process, click the name.

Accessing the Application Computation History Report

Once you create an application computation, you can view the Application Computation History report.

To access the Application Computation History report:

Navigate to the Workspace home page.
Click the Application Builder icon.
Select an application.
When Application Builder appears, click Shared Components.
Under Logic, select Application Processes.
Select History tab at the top of the page.

This Application Computation History report displays a history of recently changed application computations by date.