Calling a Form as If It Were a Function to Return a Value

• Microsoft Visual FoxPro for Windows, version 3.0

SUMMARY

In Visual FoxPro for Windows, a form is an object and as such cannot be called directly as a function can. However, by using object-oriented practices, you can create a class that calls a form. That class can in turn be instantiated in a function that returns what was entered in the form.

MORE INFORMATION

The following instructions demonstrate how to call a form as if it were a function.

1. Create a new form, and save it as MYFORM.SCX.

2. Create a text box on the form.

3. Double-click the text box to bring up the methods. Select VALID from the Procedure list, and type in the following code:

   STORE This.Value TO uRetValue

      ThisForm.Release     && release the form
   
   

4. Close the TEXT1.Valid dialog.

5. Click in the form outside of the text box to deactivate the text box. Click the right mouse button, and choose properties.

6. Select the ALL tab. Scroll down in the list to the property WINDOW TYPE.

7. Change the Window type to 1-Modal, and close the properties dialog. Then save and close the form.

8. Create and save a program file called MYTEST.PRG that contains the following code:

   *begin program

      LPARAMETERS tcfilename   && t-PARAMETER c-char
      LOCAL ofrmMyForm         && o-object (instance)
      *create an instance of the form
      ofrmMyForm=CREATEOBJECT("frmMyForm", tcfilename)
      RETURN ofrmMyForm.SHOW()
   
      DEFINE CLASS frmMyForm AS CUSTOM
           * create property to hold the filename
           cfilename=""
           FUNCTION INIT(tcfilename)
                THIS.cfilename=tcfilename
                RETURN .T.
           ENDFUNC
           FUNCTION SHOW
                PRIVATE uRetValue     && u-unknown type
                STORE .T. TO uRetValue
                * call the form
                DO FORM (THIS.cfilename)
                RETURN uRetValue
           ENDFUNC
      ENDDEFINE
      *end program
   
   

9. In the Command window, issue this command:

   ? MYTEST("MYFORM.SCX")

As the program terminates, ofrmMyForm will fall out of scope, and what was typed will show up in the active window.

This is just an example of calling a function that displays a form. With simple modification, the procedure described here could be used for password entry, prompting for a search string, or various other uses.