How to Add the Data Environment to a Form Programmatically

• Microsoft Visual FoxPro for Windows, versions 3.0 and 3.0b

SUMMARY

When a form is created using the Form Designer, a DataEnvironment object is automatically added to the form. To simulate this behavior in a programmatically created form, a DataEnvironment property must be declared for the form. Then a pointer to a DataEnvironment object may be stored in the form's DataEnvironment property.

MORE INFORMATION

1. Create a new program and type the following code:

   oform1=CREATEOBJECT("Myform") && Instantiate the form oform1.SHOW(0) oform1.refresh READ EVENTS RETURN

      DEFINE CLASS Data1 AS dataenvironment   && DataEnvironment Class
        Name = "Dataenvironment"
        ADD OBJECT "Cursor1" AS MyCursor      && ADD OBJECT for each
      ENDDEFINE                               && cursor in dataenvironment
   
      DEFINE CLASS MyCursor AS cursor         && Cursor Class
        Alias = "customer"
        Database = "C:\vfp\samples\data\testdata.dbc"
        CursorSource = "customer"
        Name = "Cursor1"
      ENDDEFINE
   
      DEFINE CLASS Myform AS form
        Top = 0
        Left = 0
        Height = 386
        Width = 587
        DoCreate = .T.
        Caption = "Form1"
        Name = "FORM1"
        DataEnvironment=""                && DataEnvironment is a property
                                          && of the form.
        PROCEDURE Destroy
          WAIT WINDOW PROGRAM() TIMEOUT 2
          THISFORM.DATAENVIRONMENT.CLOSETABLES  && Close tables at the end
        ENDPROC                                 && of destroy procedure.
   
        PROCEDURE Unload
          CLEAR EVENTS
        ENDPROC
   
        PROCEDURE Load
          * The DataEnvironment is instantiated and the form property
          * DataEnvironment references the object. The DataEnvironment
          * is never actually added to the form. THISFORM.DATAENVIRONMENT
          * is just a pointer to the DataEnvironment object.
   
          THISFORM.DATAENVIRONMENT=CREATEOBJECT("Data1")
   
          * Open the tables at the beginning of the LOAD.
          THISFORM.DATAENVIRONMENT.OPENTABLES
   
          WAIT WINDOW PROGRAM() TIMEOUT 2
        ENDPROC
      ENDDEFINE
   
   

2. Open the Debug window.

3. Type the following on the left side of the debug window

   _SCREEN.ACTIVEFORM.DATAENVIRONMENT.NAME

4. Run the program created in step 1.

5. Note that the debug window correctly displays Dataenvironment as the value of _SCREEN.ACTIVEFORM.DATAENVIRONMENT.NAME