Introduction to Multiple Form Applications

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Objectives

• Call one form from another from module• Define Multiple form functionality

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Multiple Form Applications

• Behavior:– Flexible navigation between windows– Single or multiple database connections– Transactions may span forms, if required– Commits in order of opening forms, starting with current form

• Links:– Data is exchanged by global variables or parameter lists– Code is shared as required, through libraries and the database

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Multiple Form Sessions

Form A

Forms Runtime

Global variables

Form BOpen

Form C

Open

Form D

Open

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OPEN_FORM Built-in

MDI

FORM A

MDI

FORM A

Modeless

FORM BOPEN_FORM

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Implementing Multiple Forms

1. Define windows and positions for each form.2. Plan global variables and their names.3. Implement triggers to:

• Open other forms• Initialize global variables from calling forms• Use global variables in opened forms

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Linking by Global Variables

Employees

Departments

GLOBAL.dept_id

Deptno

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Opening Another Forms

:GLOBAL.dept_id:=:DEPT.deptno;OPEN_FORM(‘employees’);

• Control passes immediately to the Employees form—no statements after OPEN_FORM are processed.

• If the Activate_Mode argument is set to NO_ACTIVATE, you retain control in the current form.

• The transaction continues unless it was explicitly committed before.

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Restricted Query at Startup

Execute_Query;

:EMP.deptno := :GLOBAL.dept_id;

When-New-Form-Instance - Form Level

Pre-Query - Block Level

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Global Variables in Opened Form

• Assign Global variables values in opened form with DEFAULT_VALUE Built-in.

• DEFAULT_VALUE ensures the existence of global variables.• You can use global variables to communicate that the form is running.

• Pre-Form Example: DEFAULT_VALUE(‘ ‘,‘GLOBAL.dept_id’);

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Conditional Opening

:GLOBAL.dept_id := :DEPT.deptno;IF ID_NULL(FIND_FORM(’EMPLOYEES’)) THEN

OPEN_FORM(’EMPLOYEES’);ELSE

GO_FORM(’EMPLOYEES’);END IF;

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Closing a Form with EXIT_FORM

• The default functionality is the same as for the Exit key.• The Commit_Mode argument defines action on uncommitted changes.

ENTER;

IF :SYSTEM.FORM_STATUS = ’CHANGED’ THEN EXIT_FORM( DO_COMMIT );

ELSE EXIT_FORM( NO_COMMIT );

END IF;

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Summary

• The OPEN_FORM built-in provides multiple concurrent forms in a session.

• Forms communicate through global variables:– Load key values in the parent form– Use global values in opened forms for

When-New-Form-Instance and Pre-Query

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