A view is a specialized object package. It is a stand-alone data-entry unit. An example of a view might be a customer entry form or an order entry form. Views are used in Windows Applications.
As more views get added to a single program, the complexity of the program will increase. If the views are allowed to interact with other views, it will become increasingly difficult to manage and maintain a large program. By making each view independent of other views, you will be able to control this complexity. A large program will merely be a collection of small programs (views).
We must be able to create and test views by themselves. When we eventually add them to the larger program, we can do so with the knowledge that the new view will not affect or be affected by other views in the program.
A view will often consist of other object packages and class packages. For example, a view will usually contain a data dictionary object structure. Each DDO defined in the structure will need a data-dictionary class and those classes are included in the view component with the use statement. In addition views will often need several object packages for lookup lists, and an object package for confirmations.
Views can be coded and tested in an object package file. The conventional file extension for view object packages is .vw.
Once a view is completed, it may be added to a program through a simple selection process within the Studio. Even if you were coding this manually, this only requires a few lines of code in a main program. This, along with a view's independence, makes it quite easy to add and remove views from a program.
The following sample shows a windows application main program. This program consists of a main menu and a series of use commands that includes the required views. Notice that the entire program is quite small.
Use DfAllEnt.pkg
Use dfPanel.pkg
Use DfAClnt.pkg
Use cHtmlHelp.pkg
Object oHtmlHelp is a cHtmlHelp
End_Object
Object oApplication is a cApplication
Set psCompany to "Data Access Worldwide"
Set psProduct to "DataFlex Examples"
Set psVersion to "12.0"
Set psProgram to "Order"
Set psHelpFile to "Examples.chm"
Set peHelpType to htHtmlHelp
End_Object // oApplication
Object oMain is a Panel
Set Label to "Order Entry Sample Application"
Set Location to 2 35
Set Size to 127 209
DFCreate_Menu Main_Menu
#Include File_PM.inc
DFCreate_Menu "&View" ViewPopupMenu is a ViewPopupMenu
On_Item "&Customer Entry View \aCtrl+1" Send Activate_oCustomerView
On_Item "&Inventory Item View \aCtrl+2" Send Activate_oInventoryView
On_Item "&Order Entry \aCtrl+3" Send Activate_oOrderEntryView
On_Item "&Sales Person Entry View \aCtrl+4" Send Activate_oSalesPersonView
On_Item "&Vendor Entry View \aCtrl+5" Send Activate_oVendorView
End_Pull_Down
Set Status_Help to "Available Views"
DFCreate_Menu "&Report" ReportPopupMenu is a ViewPopupMenu
On_Item "&Basic Report - Customer List \aCtrl+6" Send Activate_oCustomerListBR
On_Item "&WinPrint - Customer List" Send Activate_oCustomerListWP
On_Item "&WinPrint - Items per Order" Send Activate_oItemsPerOrderWP
On_Item "&WinPrint - Orders" Send Activate_oOrdersWP
On_Item "&WinPrint - Orders by Customer" Send Activate_oOrdersByCustomerWP
End_Pull_Down
Set Status_Help to "Available Reports"
#Include Navi_PM.inc
#Include Win_PM.inc
#Include HelpA_PM.inc
End_Menu
Use OrderToolbar.pkg // Tool-Bar object.
Object oClientArea is a AppClientArea
Use Customer.vw
Use Invt.vw
Use Order.vw
Use SalesP.vw
Use Vendor.vw
Use Basic\CustomerListBR.rv
Use WinPrint\CustomerListWP.rv
Use WinPrint\ItemsPerOrderWP.rv
Use WinPrint\OrdersWP.rv
Use WinPrint\OrdersByCustomerWP.rv
On_Key Key_Ctrl+Key_1 Send Activate_oCustomerView
On_Key Key_Ctrl+Key_2 Send Activate_oInventoryView
On_Key Key_Ctrl+Key_3 Send Activate_oOrderEntryView
On_Key Key_Ctrl+Key_4 Send Activate_oSalesPersonView
On_Key Key_Ctrl+Key_5 Send Activate_oVendorView
On_Key Key_Ctrl+Key_6 Send Activate_oCustomerListBR
End_Object
Use DefaultStatusbar.pkg // Status-Bar object.
Use DfAbout.pkg
Object oAbout is An AboutDialog
Set ProductName to "Order Sample Application"
Set Copyright to "Copyright: 2006 Data Access Corporation"
Set Author to "Author: Data Access Worldwide"
End_Object
Procedure Activate_About
Send Popup_Modal of oAbout
End_Procedure
End_Object
// open Order Entry view on application startup
Send Activate_oOrderEntryView of (oClientArea(oMain))
Start_UI