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4.7.2 Application Generator

 In the previous section, we created an application called employee which allows you to do data manipulation on the personnel table. The record is displayed one record per screen. In this section, we will show you how to create a multi-record display, i.e., multiple records per screen. We will use the Application Generator to create the application.

From the Empress 4GL Development Main Menu, press the Application Generator key. The Application Generator Main Menu is displayed:

Figure 4-72 Application Generator Main Menu Figure 4-72 Application Generator Main Menu

Press the Create key and enter employee2 as the new definition name.

Figure 4-73 employee2 application Figure 4-73 employee2 Application

Press the <Return> key and the following screen appears:

Figure 4-74 Data Entry Application Figure 4-74 Data Entry Application

Move the cursor to DATA SET.

When the <Return> key is pressed, you will see a small window to the right of your selection.

Figure 4-75 DATA SET Figure 4-75 Data Set

Move the cursor to TABLES and press <Return>, the screen should look like this:

Figure 4-76 Tables Figure 4-76 Tables

Press the List Tables key:

Figure 4-77 List Tables Figure 4-77 List Tables

Since there is only one table in the example, we can press the Choose All key.

Figure 4-78 Choose All Figure 4-78 Choose All

If there are more than one table in the database, they would have been listed in the TABLES list and you would select the names of each table you want to include in you application by moving the cursor to it and pressing the <Return> key. Note that the Application Generator allows you to generate a screen interface application based on more than one table. For more detailed information, please refer to the Empress 4GL: Tools Reference manual.

Press the Quit key twice to return to this screen:

Figure 4-79 DATA SET Figure 4-79 Data Set

Press the Quit key and move the cursor to CREATE APPLICATION and press <Return>. This will create an application called employee2.

Move the cursor to RUN APPLICATION and press <Return>. You will see the same personnel application presented in a different format. Instead of one record per screen as created by the Default Application Generator, it is now in the multi-record display format.

Figure 4-80 employee2 application multi-record display Figure 4-80 employee2 Application Multi-record Display

Press the Quit key to exit the application. Move the cursor to EXIT and press <Return>. You will see the following screen:

Figure 4-81 Save the Application Generator Definition Figure 4-81 Save the Application Generator Definition

At this point, the application is created and the Application Generator (AG) is asking if you would like to save this definition. The "definition" refers to the Application Generator's descriptive representation of how to build the application it just built for you. Saving this definition now will enable you to return to the Application Generator later to modify the application rather than using the Application Editor. If you wish to save the definition for later modifications, enter "y". If not, enter "n". In this example, we will enter "n". This will take you to the Application Generator Main Menu.

Press the Quit key to return to the Empress 4GL Main Menu.


4.7.2.1 Forms

 The Application Generator will first create three forms called employee2_form1, employee2_help and employee2_menu. All the forms created are prefixed with the application name.

The form employee2_form1 is created based on the Application Generator SET UP PARAMETERS and DATA SET:

Figure 4-82 employee2_form1 Figure 4-82 employee2_form1

The SET UP PARAMETERS for the employee2 specifies:

  1. The display type is Column,
  2. The number of records to display per page is 10.
  3. The field labels are Left justified. 

    Figure 4-83 SET UP PARAMETERSFigure 4-83 Set Up Parameters

The DATA SET for the employee2 specifies:
  1. The table name to be used is personnel.
  2. The attributes from the personnel table are credit_limit, name, number, and phone. 

    Figure 4-84 DATA SET attributesFigure 4-84 Data Set Attributes

The form employee2_menu is created to display the function keys for select, insert, update, etc.

Figure 4-85 employee2_menu Figure 4-85 employee2_menu

The form employee2_help is used for the Help window for each attribute as indicated by the INTERFACE/SCREEN definition.

Figure 4-86 INTERFACE Figure 4-86 Interface

To have help available on a per-attribute basis, change the N to Y in the Help column beside the attributes for which help will be available. Each time you change an N to a Y, you will be given the opportunity to type in a few lines that will be displayed when the Help key is pressed while this field is current.

By default, the Application Generator does not create Help for each attribute.

Figure 4-87 INTERFACE screen Figure 4-87 Interface Screen


4.7.2.2 Application Enter Script

When you run the employee2 application, the following Application Enter Script is executed:

Figure 4-88 Application Enter Script Figure 4-88 Application Enter Script

The following are the detailed explanations of each statement in the APPLICATION TABLE Enter Script: 

call show_window ('employee2_menu');
call set_key_values ('employee2_menu');
These two statements display the employee2_menu window and assign the function keys to it based on the terminal type that you are using. The employee2_menu window is defined in the WINDOW TABLE.

Figure 4-89 employee2_menu window Figure 4-89 employee2_menu Window 

call show_window ('employee2_form1');
This statement displays the employee2_form1 window which is defined in the WINDOW TABLE.

Figure 4-90 employee2_form1 window Figure 4-90 employee2_form1 Window 

call current_window ('employee2_form1', 't1_a1');
This statement assigns employee2_form1 as the current window and the field t1_a1 as the current field. t1_a1 is the field corresponding to the number attribute in the table. It is chosen as the current field because it is closest to the top left corner of the form. 
call 'employee2_open_script' ();
This statement calls a subscript which is defined in the SCRIPT TABLE.

Figure 4-91 employee2_open_script Figure 4-91 employee2_open_script

This script opens the personnel table in update mode and assigns employee2_t1 as the table instance name. 

call 'employee2_multi_script' ();
This statement calls the employee2_multi_script subscript which is defined in the SCRIPT TABLE.

Figure 4-92 employee2_multi_script Figure 4-92 employee2_multi_script

employee2_multi_script does the following:

  1. It declares a local integer variable called rows.
    2. local
   integer rows;
end;
  2. It calls a subscript employee2_select_script which is defined in the SCRIPT TABLE.
    3. call 'employee2_select_script ()';
    The employee2_select_script defines a select statement and assigns employee2_ctxt as a context name.

    The define select is different from the regular select only in that the select is not actually run when the define select statement is executed. 

    Figure 4-93 employee2_select_script Figure 4-93 employee2_select_script

  3. It associates a context with a window for multiple record displays.
    4. let rows = largest_field_number ('employee2_form1', 't1_a1');

call define_multi ('employee2_ctxt', 'employee2_form1', rows, 1,
   'employee2_display_script',
   'employee2_lock_script',
   'employee2_fill_script');
    It also associates several scripts with the window and context for maintaining the multi-record display.

    The employee2_display_script assigns the attribute values to the fields. 

    Figure 4-94 employee2_display_script Figure 4-94 employee2_display_script

    The employee2_lock_script defines the action to be taken when a locked record is encountered. 

    Figure 4-95 employee2_lock_script Figure 4-95 employee2_lock_script

    The employee2_fill_script defines the action to be taken when there is no record to display. 

    Figure 4-96 employee2_fill_script Figure 4-96 employee2_fill_script

    Now, back to employee2_multi_script.

  4. It selects the data and displays data on the screen:
    5. select context 'employee2_ctxt'
call display_page ('employee2_ctxt');


4.7.2.3 Field Enter and Exit Scripts

In a multi-record display, the form contains arrays of fields for each attribute that is to be displayed. If the definition for each field in an array is the same, then they may be defined in the Field Table with a single entry as follows:

Figure 4-97 t1_a1 Figure 4-97 t1_a1

Notice that we use "0" as the field number. This means that all fields in the window employee2_form1 with the name t1_a1 have this definition.

In our example, the fields t1_a1, t1_a2, t1_a3 and t1_a4 will have a similar entry in the Field Table.

Figure 4-98 t1_a2 Figure 4-98 t1_a2

Figure 4-99 t1_a3 Figure 4-99 t1_a3

Figure 4-100 t1_a4 Figure 4-100 t1_a4


4.7.2.4 Key Scripts

The key scripts for employee2 are defined in the KEY TABLES. They are:

Figure 4-101 Select Key Figure 4-101 Select Key

Figure 4-102 Next Key Figure 4-102 Next Key

Figure 4-103 Previous Key Figure 4-103 Previous Key

Figure 4-104 Insert Key Figure 4-104 Insert Key

Figure 4-105 Update Key Figure 4-105 Update Key

Figure 4-106 Delete Key Figure 4-106 Delete Key

Figure 4-107 Clear Key Figure 4-107 Clear Key

Figure 4-108 Next Page Key Figure 4-108 Next Page Key

Figure 4-109 Previous Page Key Figure 4-109 Previous Page Key

There are two subscripts called from keys in the context employee2_ctxt: employee2_attr_script and employee2_clear_script. Both of them are defined in the SCRIPT TABLE.

The employee2_attr_script assigns the field values to the attributes.

Figure 4-110 employee2_attr_script Figure 4-110 employee2_attr_script

The employee2_clear_script clears all the fields in the window by assigning NULL to the fields.

Figure 4-111 employee2_clear_script Figure 4-111 employee2_clear_script


4.7.2.5 Application Exit Script

When you exit the application, the Application Exit Script is executed (defined in the APPLICATION TABLE).

Figure 4-112 Application Exit Script Figure 4-112 Application Exit Script

The script calls for a subscript employee2_close_script which is defined in the SCRIPT TABLE.

Figure 4-113 employee2_close_script Figure 4-113 employee2_close_script

employee2_close_script removes all the windows from the screen, undefines the select context and closes the table.

After executing the Application Exit Script, the control returns back to the calling application or operating system.



4.8 Print Application

 Empress 4GL provides a utility to print the application source code. The command is emp4prt: 
emp4prt database application
where:

database is the name of a database.
application is the name of an application.

The output can be redirected to a file. For example, to print the employee application, type in the following command at the system level:

   emp4prt repairs employee > filename