Q128996: HOWTO: Assign Database Location Generically in Data Env

Article: Q128996
Product(s): Microsoft FoxPro
Version(s): 
Operating System(s): 
Keyword(s): kbnokeyword kbvfp300 kbvfp500 kbvfp600
Last Modified: 09-AUG-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 5.0, 6.0 
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SUMMARY
=======

The Data Environment contains information about all the tables, views, and
relationships that interact with a form. In the Form Designer, when a table is
added to the data environment, the database property of a cursor is updated with
the location and name of the DataBase container (.DBC), and the path written in
the DataBase property is set by default as an absolute path.

If the database cannot be found when the form is opened, the error "Error
instantiating cursor object. Cannot find ..<database>" is displayed.

The sample code provided in this article modifies the path information written in
the Database property to fit your needs.

MORE INFORMATION
================

When a table is added to the Data Environment in the Form Designer, a cursor
object is created. If the table belongs to a DBC, the DataBase property of the
cursor is updated with the full path name to the DBC. However, the absolute path
to a DBC might need to be modified in a distributed application. For example,
multiple users can open databases with the same name that are placed in
different locations.

If you need to reference a different database than the one specified in the
Database property of the Cursor object, you can use the SET PATH command, before
the program calls the form, to set a path to the location of the database. If
the database specified in the DATABASE property of the Cursor cannot be found,
Visual FoxPro will search along the path.

Another alternative is to update the DATABASE property at runtime. The following
example adds flexibility to your code by updating the path information in the
Database property of the cursor object. This code can update the location of
different databases referenced in the Data Environment. As this sample only
references one directory, you will need to modify it if you need to open
databases in several directories.

To use this example:

1. Create two variables that will be available to the form - Data_Drive. This
  variable contains the drive letter and a colon.

  Data_Drive = "C:"

  - Data_Path. This variable contains the relative path with a backslash as the
  last character.

  Data_Path = "\VFP\SAMPLES\DATA\"

2. Place the following code in the BeforeOpenTables Event of the
  DataEnvironment. The WAIT WINDOW commands are for illustrating purposes, and
  you can remove them.

        IF !EMPTY(DATA_PATH) and !EMPTY(DATA_DRIVE)
          * Make a list of all the cursors in the Data Environment
           =AMEMBERS(A_Cursors,THISFORM.dataenvironment,1)
           =ASORT(A_Cursors, 2)
           nStartpos=ASUBSCRIPT(A_Cursors, ASCAN(A_Cursors, "Object"),1)
           FOR I = nstartpos TO ALEN(A_cursors,1)
             IF A_Cursors(i,2) = "Object"
              cObjClass = "THISFORM.DATAENVIRONMENT."+a_cursors(i,1)+".class"
                IF EVAL(cObjClass)="Cursor"
                 cObjName="THISFORM.DATAENVIRONMENT." ;
                      + A_Cursors(i,1)+".DATABASE"
                 WAIT WINDOW cObjName
                 Data_Name=EVAL(cObjName)
                 WAIT WINDOW "This is Data_Name : "+ Data_Name
                 * Modify the path to the database
                 NewDataPath=ALLTRIM(data_drive)+ ALLTRIM(data_path) ;
                      + ALLTRIM(SUBSTR(Data_Name, RAT("\",Data_Name)+1))
                 WAIT WINDOW newdatapath
                 * Evaluate the cursor object
                 oRef = EVAL( "THISFORM.DATAENVIRONMENT."+a_cursors(i,1) )
                 *Modify the Database property with the new path
                 oRef.Database = newdatapath

                ENDIF
                ELSE
                 EXIT
             ENDIF
           ENDFOR
        ENDIF

Additional query words:

======================================================================
Keywords          : kbnokeyword kbvfp300 kbvfp500 kbvfp600 
Technology        : kbVFPsearch kbAudDeveloper kbVFP300 kbVFP500 kbVFP600
Issue type        : kbhowto

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