This document discusses how to implement multiple form applications in PowerBuilder. It describes using the OPEN_FORM built-in to call one form from another, sharing data between forms through global variables, and transaction management across multiple concurrently open forms. Forms can exchange data via global variables or parameter lists defined in the database. Navigation between forms is flexible and transactions may span multiple forms as required.

1. Introduction to Multiple Form Applications
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2. Objectives
• Call one form from another from module
• Define Multiple form functionality
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3. 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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4. Multiple Form Sessions
Form A
Forms
Runtime
Global variables
Form B
Open
Form C
Open
Form D
Open
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5. OPEN_FORM Built-in
MDI
FORM A
MDI
FORM A
Modeless
FORM B
OPEN_FORM
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6. 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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7. Linking by Global Variables
Employees
Departments
GLOBAL.dept_id
Deptno
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8. 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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9. 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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10. 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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11. 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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12. 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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13. 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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