HOWTO: Alter the Properties of a View at Run Time

• Microsoft Visual FoxPro for Macintosh, version 3.0b
• Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 5.0a

SUMMARY

Under some circumstances, it may be desirable to modify the properties of a view at run time. This article describes the properties and default property values associated with a view. The sample code illustrates how to create a view and use the DBSETPROP() function to alter the properties of the view programmatically.

MORE INFORMATION

The properties of a view created with the View Designer are readily accessible from the View Designer. The properties of a view created programmatically, however, use default values unless those values are changed either programmatically or from the View Designer.

The default values of a view created programmatically are as follows:

   Property Name            Default Value
   --------------------------------------

   SendUpdates              .F. (False)
   UpdateType               1 SQL Update
   WhereType                3 Key and Modified Fields
   BatchUpdateCount         1
   UseMemoSize              255
   FetchSize                100
   FetchMemo                .T. (True)
   MaxRecords               -1 (All)
   Tables                   Database Container and Table Name
   Comment                  Null String
   Prepared                 .F. (False)
   CompareMemo              .T. (True)
   FetchAsNeeded            .F. (False)


   View Field Properties    Default Value
   -------------------------------------

   KeyField                 .T. (True if the field is a Primary Key)
                            .F. (False if the field is not a Primary Key)
   Updatable                .F. (False)
   UpdateName               Database Container, Table Name And Field Name
   DataType                 Same as source field
   Caption                  Null String
   RuleExpression           Null String
   RuleText                 Null String
   Default                  Null String

   Prepared
   CompareMemo
   FetchAsNeeded

1. Create a program called Makeview.prg using the following code:

         thisversion=VERSION()
         IF LEFT(ALLTRIM(thisversion),6)="Visual"
           thisversion=VAL(SUBSTR(thisversion,15,2))
         ELSE
           thisversion=0
         ENDIF
         SET EXCLUSIVE ON
         SET MULTILOCKS ON
         OPEN DATABASE home()+"\SAMPLES\DATA\TESTDATA"
         CREATE SQL VIEW customerview ;
          AS SELECT DISTINCT cust_id, company, contact ;
         FROM testdata!customer ;
         ORDER BY customer.cust_id
         * Set view properties.
         =DBSETPROP('CUSTOMERVIEW','View','SendUpdates',.T.)
         =DBSETPROP('CUSTOMERVIEW','View','UpdateType',2)
         =DBSETPROP('CUSTOMERVIEW','View','WhereType',1)
         =DBSETPROP('CUSTOMERVIEW','View','BatchUpdateCount',3)
         =DBSETPROP('CUSTOMERVIEW','View','UseMemoSize',255)
         =DBSETPROP('CUSTOMERVIEW','View','FetchSize',100)
         =DBSETPROP('CUSTOMERVIEW','View','FetchMemo',.T.)
         =DBSETPROP('CUSTOMERVIEW','View','MaxRecords',10)
         =DBSETPROP('CUSTOMERVIEW','View','Tables','CUSTOMER')
         =DBSETPROP('CUSTOMERVIEW','View','Comment',"Demonstration View")
         IF thisversion>=5
         =DBSETPROP('CUSTOMERVIEW','View','Prepared',.F.)
         =DBSETPROP('CUSTOMERVIEW','View','CompareMemo',.T.)
         =DBSETPROP('CUSTOMERVIEW','View','FetchAsNeeded',.T.)
         ENDIF
         SELECT customer
         USE
         * Set Key and Updatable fields.
         =DBSETPROP('CUSTOMERVIEW.Cust_id','Field','KeyField',.T.)
         =DBSETPROP('CUSTOMERVIEW.Cust_id','Field','Updatable',.T.)
         =DBSETPROP('CUSTOMERVIEW.Cust_id','Field','UpdateName', ;
         'CUSTOMER.Cust_id')
         =DBSETPROP('CUSTOMERVIEW.Cust_id','Field','DataType',"C(12)")
         =DBSETPROP('CUSTOMERVIEW.Cust_id','Field','Caption','Primary Key')
         =DBSETPROP('CUSTOMERVIEW.Company','Field','KeyField',.F.)
         =DBSETPROP('CUSTOMERVIEW.Company','Field','Updatable',.T.)
         =DBSETPROP('CUSTOMERVIEW.Company','Field','UpdateName', ;
         'CUSTOMER.Company')
         =DBSETPROP('CUSTOMERVIEW.Company','Field','DataType',"N(15,2)")
         =DBSETPROP('CUSTOMERVIEW.Company','Field','Caption','Company Name')
         =DBSETPROP('CUSTOMERVIEW.Contact','Field','KeyField',.F.)
         =DBSETPROP('CUSTOMERVIEW.Contact','Field','Updatable',.F.)
         =DBSETPROP('CUSTOMERVIEW.Contact','Field','UpdateName', ;
         'CUSTOMER.Contact')
         =DBSETPROP('CUSTOMERVIEW.Contact','Field','DataType',"N(15,2)")
         =DBSETPROP('CUSTOMERVIEW.Contact','Field','Caption','Contact Name')
         USE customerview
         BROWSE
         RETURN
   
   

2. From the Command window, type:

         DO Makeview.prg
   

   The program creates an updateable view based on the Customer table.