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Control Forms

Overview

There are occasions when a single logical transaction requires data from several forms. It is possible to use a parent form and a series of child auxiliary forms, but this requires that each auxiliary form returns to the parent form before the user can select the next form.

A Control form is a special type of parent for a group of auxiliary forms. It has the following characteristics:

• The Control form has no dialog with the user (it is classed as hidden or invisible).
• It contains a list of child forms which are activated one at a time in a predefined sequence.

A mixture of a Control form and Auxiliary forms can be constructed as shown in Figure 1.

Figure 1 - A Control form with Auxiliary forms

The solid arrows show what the user sees. The dotted arrows show what actually happens.

This arrangement has the following characteristics:

• The transaction begins and ends within the parent Control form. This is the form that is selected from the Menu system, or from a navigation button in the parent form.
• All database access (reading and updating) is performed within the Control form.
• After updating the database the form will send a message to its parent so that the parent can update its contents accordingly.
• All data is held within the Control form, with subsets being passed to child forms when required. This data is passed as a parameter on an operation (by default the EXEC operation).
• If the auxiliary form allows data to be changed it is passed back to the parent as an argument on an operation (usually the UPDATE operation).
• The Control form contains a list of child forms that it can activate.
• When the Control form is selected it automatically activates the first child form in its list.
• When the last child form in the list has completed the Control form will update the database (if required) then terminate.
• All child forms will be activated as MODAL (i.e. any non-modal settings will be turned off).

The following options are also available:

• When the last form has been completed there is the option to either update the database and terminate, or return to the first form in order to review the data and make changes.
• Each form may have a command button which returns to the previous form rather than only being able to go to the next form.
• Logic can be inserted into the Control form to change the list of child forms at run time according to data values. Forms can be added to the list, removed from the list, or one form can be changed for another.

The <EXEC> proc contains code which will initialise its data using any initial values that have been defined for the control form as well as all the forms in component variable $form_list$.

Before each child form is activated LP_PRE_PROC is available for pre-processing.

After returning from each child form LP_POST_PROC is available for post-processing.

The following operations are also available:

• UPDATE (FromComponentName, ReturnData) - used by a child form to return updated data.
• NEXTFORM (FromComponentName, NextForm) - used by a child form to override the identity of the next form.
• PREVIOUSFORM (FromComponentName) - used a by a child form to set the identity of the next form to what was the previous form in the current sequence.

Control 1 - add an occurrence

Description

For an overview of all Control forms please go here.

This form is used to create a new occurrence of a single MAIN entity. All screen dialog is performed by a series of child forms which have their identities listed in component variable $FORM_LIST$. All data is passed back from the child forms to the parent control form for updating on the database.

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Control 2 - add a MANY in a ONE-to-MANY relationship

Description

For an overview of all Control forms please go here.

This form is used to create a new occurrence of a MANY entity in a ONE to MANY relationship. The identity of ONE must be passed as a parameter when the form is first activated. All screen dialog is performed by a series of child forms which have their identities listed in component variable $FORM_LIST$. All data is passed back from the child forms to the parent control form for updating on the database.

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

Control 3 - read/write access

Description

For an overview of all Control forms please go here.

This form is used to modify the details of a selected occurrence of entity MAIN. It will retrieve the selected occurrence, then pass the data to a series of child forms which have their identities listed in component variable $FORM_LIST$. These forms will display the data and allow modifications. All data is passed back from the child forms to the parent control form for updating on the database.

Contents

Bound Objects

Local Constants (Refer to Local Constants)

Component Variables (Refer to Component Variables)

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