How to Programatically List .VCX File's Class Definitions

• Microsoft Visual FoxPro for Windows, version 3.0

SUMMARY

A Visual Class Library (VCX) contains references to classes. This article provides two methods that will allow you to list the name of the classes contained in a class library.

MORE INFORMATION

The Visual Class designer provides an interface that allows you to create classes visually. The class definitions are stored in a table with a .VCX extension. Although there is no native Visual FoxPro command that will allow you to list all the classes saved in a .VCX file, there are ways to retrieve this information.

Use the VCX as a Table

A VCX is a FoxPro table, so you can open it with the USE command, and you can manipulate the table as if it were a .DBF file. When a class is created, a new record is added for each object that belongs to the class. Additionally, the first record for the class contains information about the class definition, and the Reserved1 field of the .VCX file contains the word "Class" to tag a class definition. It is therefore possible to query the table for these records that have the Class string in the Reserved1 field. The following example queries the LOGIN.VCX file located in the SAMPLES\MAINSAMP\LIBS directory; it retrieves the name of class definitions.

   olddir=CURDIR()
   CD SYS(2004)+"SAMPLES\MAINSAMP\LIBS"
   IF NOT USED('LOGIN.VCX')
      USE LOGIN.VCX NOUPDATE
      ELSE
      SELECT LOGIN.VCX
   ENDIF

   SELECT PADR(objname,20) FROM LOGIN.VCX WHERE Reserved1=='Class' ;
     INTO ARRAY myarray
   = MESSAGEBOX ("There are "+ALLTRIM(str(alen(myarray)))+ " classes")
   CD EVALUATE('olddir')

Use the Class Browser

In development mode, you can use the Class Browser to list the classes in a .VCX file. To do so:

1. Run the Class Browser and open the VCX you need. You can open the Class Browser by choosing Class Browser from the Tools menu and selecting the library. You can also type the following from the Command window:

   DO (_BROWSER) WITH <library>

2. Run the following code. When the Class Browser is loaded, the _Obrowser instance variable is created. It references the Browser object. The _oBrowser object contains a two dimensional array member (aclasslist) that lists the elements of a class. The fist element contains the name of the class. You can therefore list the classes stored in a VCX by running this code:

   DO (_BROWSER) with "c:\vfp\samples\mainsamp\libs\login.vcx" nArraylen=ALEN(_obrowser.aclasslist,1) &&How many classes * The first element of the array is ignored because it contains * information about the class library. DIMENSION arrayclass(narraylen-1) FOR I=2 to narraylen

          arrayclass(I-1)=_obrowser.aclasslist(I,1)
   

   ENDFOR ACTIVATE SCREEN DISPLAY MEMO like ARRAYCLASS

REFERENCES

For more information about the Class Browser, search for "_BROWSER" and "Sample Files" topics in the Visual FoxPro Help menu.