CHAPTER 3: The Application Generator

• choose the way records are displayed: as one record per screen or multiple records displayed in columns or rows with wraparound
• choose the tables to be accessed
• choose the attributes to be accessed
• have output sorted by any attribute(s)
• have data selection based on specified qualifications, for example, matching a constant, or a join condition
• choose the database operations available to the application user, for example by allowing SELECT, INSERT, UPDATE, DELETE
• customize the screen display by choosing the title, number of screens and field labels
• choose the returned values to be displayed
• link applications to form larger systems with hierarchies of menus

For example, when an application called loansinfo is created using the Application Generator, the following menu appears on the screen:
 
Figure 3-1 Main Menu

If you move the cursor to Loan List and press <Return>, an application based on the loans and personnel table is run. It displays the name, date, and amount from the loans table and the corresponding phone and credit_limit from the personnel table. It is also restricted to read only information.

If you move the cursor to Loans Table and press <Return>, an application is run which displays a window from which you can select, update and delete information in the loans table.

If you move the cursor to Personnel Table and press <Return>, an application which displays a window from which you can select, update and delete information in the personnel table.

To create this application, follow these steps:

Step 1

Create the application called loansinfo using the Application Generator and define the Menu Definition as:
 

Step 2

Create the loanlist application using the Application Generator to define:

• Data Entry Definition
• screen output in columnar format
• number of records displayed per page is 10
• left justified field labels
• read only data

Create two default applications with the names loans and personnel.

At this stage, you have completed your application development.

In the previous section, we discussed how to create a default application. In the next few sections, we will show you step by step how to create the loanlist and loansinfo applications using the Application Generator.

In this screen, the Application Generator lists the names of the Data Entry Definitions and Menu Definitions if there are any. You can edit an existing definition or create a new definition. It also allows you to copy, delete and rename the applications.

Press the Create key and enter the Data Entry Definition name as loanlist on the following screen:
 
Figure 3-3 loanlist

Since the application loanlist will be generated based on the definition, it is easier to name the Data Entry Definition with the same application name.

When the <Return> key is pressed, you will enter the Data Entry Definition menu screen:
 
Figure 3-4 Data Definition Menu

From this menu you can invoke the following functions:

Table 3-1
 

Option	Function
EMPRESS SQL	Escapes to an Empress SQL session.
SET UP PARAMETERS	Determines how fields will appear on the screen.
DATA SET	Chooses tables and attributes to be used in the application. It also determines sort order and select conditions.
INTERFACE	Chooses the functions to be made available, the field labels that will appear on the screen, and other details of the screen display.
CREATE APPLICATION	Confirms your choices for the application definition and creates the application.
RUN APPLICATION	Runs the application.
EXIT	Exits to the Application Generator Main Menu.

When you move your cursor to the SET UP PARAMETERS field and press <Return>, you can define how fields will appear on the screen:
 
Figure 3-5 Setup Parameters

3.2.1 Type of Display

"Row" produces a display like the following, with one record per screen:

    record1  label1: field1

             label2: field2

             label3: field3

             label1  label2  label3

    record1  field1  field2  field3

    record2  field1  field2  field3

    record1  label1: field1 label2: field2

             label3: field3

    record2  label1: field1 label2: field2

             label3: field3

3.2.2 Number of Records to Display per Screen

3.2.3 Justify Field Labels

"Right" justification creates a display like this:

                        name:

                        date:

                      amount:

                       phone:

                credit_limit:

            name:

            date:

           amount:

            phone:

        credit_limit:

name:

date:

amount:

phone:

credit_limit:

When you complete the set up, press the Quit key (obtained from the Help screen) to return to the Data Entry Definition menu.

Move the cursor to Tables and press <Return> and the following screen appears:
 
Figure 3-7 Table Selection

You may choose from tables in the current database, by pressing the List Tables key:
 
Figure 3-8 List of Tables

You can press the Choose All key to choose all the tables or move the cursor to fields under the listing of TABLES and press <Return>. The table name(s) which you have chosen will appear in the listing of the TABLES CHOSEN.
 
Figure 3-9 Tables Chosen

Press the Quit key to return to the TABLE SELECTION screen and press the Quit key again to return to the Data Entry Definition menu.

From here you can:

Table 3-2
 

Options
Create Attr	Choose the attributes to be in the application.
Delete Attr	Remove attributes not required in the application.
List Tables	Lists the tables and attributes available.
Delete All	Deletes the entire list of ATTRIBUTES CHOSEN.
Choose All	Chooses the entire list of attributes available for the current application.

Carefully examine the SELECT statement:

    SELECT name, date, amount, phone, credit_limit

         FROM loans, personnel

         WHERE loans.name = personnel.name

         SORT BY date;

Press the Quit key to return to the Data Entry Definition menu.

From this screen, you can choose the attributes by which your output will be sorted. By assigning numbers to attributes, with 1 representing the first sorted attribute, the output will be sorted in the specified order.

In this case, move the cursor to the date field and type in 1.
 
Figure 3-13

Press Quit to return to the Data Entry Definition menu.

This is the screen from which you may specify the WHERE clause for the SELECT statement. For example:

    WHERE loans.name = personnel.name

Move the cursor to the attribute name of the loans table and press <Return>. It shows the table loans and the attribute name.
 
Figure 3-16

Move to the next field (press the NEXT_FIELD key) and the available operators are listed:
 
Figure 3-17

Choose "=" by moving the cursor to "=" then press <Return>.
 
Figure 3-18

This is to specify an item on the right hand side of the operator, i.e., loans.name = ? where "?" can be a constant or another attribute. In this case move the cursor to ATTRIBUTE and press <Return>.
 
Figure 3-19

Again, move the cursor to name from the personnel table and press <Return>.
 
Figure 3-20

Now you have completed the QUALIFICATION SELECTION.

Press the Quit key to return to the Data Entry Definition menu and press the Quit key again to remove the DATA SET sub-menu.

Move the cursor to FUNCTIONS and press <Return>.
 
Figure 3-22 Function Key Definition

From here the following functions are available:

Table 3-3
 

Options	Function
Delete	Removes a function and its associated label and key from the function list.
Functions	Lists and selects from the functions available. They are: Select, Insert, Update, Delete, Clear, Next, Previous, Call Appl/Menu, and Reserved.
Tables	Lists the available tables; you may select those for which the functions will be available.
Keys	You can assign a function key to each function. When you press these keys, Empress 4GL will perform the function associated with that function key.
Labels	You can also choose labels for the functions. Labels and their associated keys appear in a menu at the bottom of the application screen.

In this example, for this application to have read only functionality, move the cursor to the Insert field and press the Delete key. Follow the same steps to delete the Update and Delete function keys.
 
Figure 3-23

Press the Quit key to return to the Data Entry Definition menu.

At this point, the cursor is in the Page Label field. To move to the (TABLE) ATTRIBUTE area, press the `Edit Attributes' Menu key. Now the cursor is in the (TABLE) ATTRIBUTE area from which the following functions are available:
 
Figure 3-25

Table 3-4
 

Options
List Attr	Lists the available attributes.
Delete	Removes an attribute from the screen display.
Add Attribute	Selects an attribute to appear in the screen display.
`Edit Page' Menu	Change back to creating new pages and editing page headings which appear on top of pages. Multi-record applications can only have one page.

Since loans.name and personnel.name are the same thing, we can delete one of them from the display screen. Move the cursor to (personnel) name field and press the Delete key to remove it from the list.
 
Figure 3-26

Whenever the cursor is moved to the OPERATOR field, the following screen is displayed:
 
Figure 3-27

When you press the Select key, the selection criteria as defined in this menu will be evaluated.

The label for the attribute value is the default attribute name. You can modify the label for a more presentable format.
 
Figure 3-28

You may also modify the width of the display area or add a brief help message for each field. Once you have the completed the modification, press the Quit key to return to the Data Entry Definition menu.

Note

If the window is not big enough for the data to be displayed in columnar format, it will be displayed in block format. The forms and the script that were generated by the Application Generator can be modified through the Form Manager and Application Manager.

At this point, we have completed the loanlist application. You can run the application or exit the Data Entry menu. To exit, move the cursor to EXIT and press <Return>. You will see:
 
Figure 3-29

You can save this definition by answering y at the prompt.

To create a menu linking two or more applications, move the cursor to the field Menu Definition from the Application Generator Main Menu and press Create key. The following screen will appear:
 
Figure 3-30 Application Generator

Enter the name of the Menu Definition beside the prompt "Enter the name of a new AG definition:"

In this example, type in loansinfo. When the <Return> key is pressed, this is what you will see on the screen:
 
Figure 3-31

Move the cursor to DEFINE MENU and press <Return>. The following screen appears:
 
Figure 3-32

This is where you start to build a hierarchical menu system. Each item on the menu has the ability to call other menus or applications from the next level.

For example:

Our example is a simple one:

• Loan List calls the application loanlist
• Loans Table calls the application loans
• Personnel Table calls the application personnel

Enter loanlist and press <Return>. This is what appears on the screen:
 
Figure 3-33

Move the cursor to the M/A field then move the cursor from the MENU field to the APPLICATION field.
 
Figure 3-34

Change the LABEL field to Loan List. This is what will appear on the screen:
 
Figure 3-35

Apply the same steps to the other two items.
 
Figure 3-36

Once this is done, press the Quit key to return to the Menu Definition menu. Move the cursor to CREATE MENU and press <Return>. This will create the menu definition. When this is done, move the cursor to RUN MENU and the following screen appears:
 
Figure 3-37

When you exit the Menu Definition menu, you can decide whether or not to save this Menu Definition. If you do, this definition can be edited and modified through the Application Manager and the Form Manager.
 
Figure 3-38

Press the Quit key to return to the Application Generator Main Menu. You can save the definition by answering y at the prompt.