Class and Object Names

These are some notes from our design manual for your possible use and/or amusement. :-) There is not a lot new here but you may be interested in the way we pulled things together.

Note I set the FoxPro beautify tool to convert reserved words to lower case and symbols to match the first occurence.


Class and object names have no scope or type prefix but they should be preceeded with a three-letter prefix which denotes their function or base class. Since the prefix designates the function of the class, don't repeat this information. For example avoid ChkCheckBox1 in favor of ChkAuditReport. Or consider this horrible example from the Foxpro Help for the AddObject method:

Bad: frmMyForm.AddObject('cmdCmndBtn1','cmdMyCmndBtn1') && Up Cmnd button

Good: FrmMyOwn.AddObject('cmdUp','CmdBasic') && Up command button

You may wish to start class names with a capital letter and object names that do not match any class name with a lower-case letter.

See also Advanced Object Oriented Programming with Visual FoxPro 6.0 by Markus Egger (pages 237-244) for his take on naming conventions. The prefixes below match his very closely.

Unlike Marcus and the Codebook folks we do not make a naming distinction between a class and an object. Generally we think of an 'object' as being an instance of a class so they both get the same name unless there is more than one instance and then the extra objects get variations or more specific names.

For this reason we do not use 'C' for concrete class or 'A' for abstract class as others do. Also note that a variable which contains a pointer to an object of any class has type 'o' following the appropriate scope character or object name.

When we instantiate an application as a standalone object we store the reference to that object in a global variable called 'goApp'. Note: many people use 'oApp' for this.

If we place a business object in a form we might (depending on the context) refer to the business object as thisform.BizPeople (for example). If this form has a child form for the address we might refer to the city field on the Address form as: thisform.BizPeople.BizAddressCh.txtCity. Note that it is no use typing 'ThisForm' because the Beautify tool will soon change it to lower case.

Prefix Characters for Common Classes

General Function       Pref Base Class      Comment
Active Document         Acd activedoc   
Application             App container       Main application class
Data Behavior Object    Bhv container       Data behavior logic
Business Object         Biz container       Business logic
Button                  Btn commandbutton   Small button on a toolbar
Check Box               Chk checkbox    
Collection              Col collection  
Column                  Grc column  
Combo Box               Cbo combobox    
Command Button          Cmd commandbutton   Larger button with a caption
Command Group           Cmg comandgroup 
Container               Cnt container       Control Ctl control 
Cursor                  Cur cursor  
Custom                  Cus custom  
Data Environment        Env dataenvironment 
Edit Box                Edt editbox 
Form                    Frm form    
Form Set                Frs formset 
Graphical User Inter.   Gui container       Contains controls & little code.
Grid                    Grd grid    
Header                  Grh header          Grid header. 
Hyperlink               Hyp hyperlink   
Image                   Img image   
Label                   Lbl label   
Line                    Lin line    
List Box                Lst listbox 
Manager                 Mgr custom  
Menu                    Mnu container   
Menu Bar                Bar container   
Menu Pad                Pad container   
Middle Tier Class       Mid custom  
Miscellaneous Class     Cls relation    
OLE Container Control   Ole OLEcontrol  
OLE Bound Control       Olb OLEboundcontrol 
Option Button           Opt optionbutton    
Option Group            Opg optiongroup 
Page                    Pag page    
Page Frame              Pgf pageframe   
Project Hook            Pjh projecthook     
Pop-up Form             Pop SCX (1)         SCX form with ShowWindow = 1
Relation                Rel relation        When actually used as relation.
Separator               Sep separator   
Session                 Ses session 
Shape                   Shp shape   
Spinner                 Spn spinner 
SPT Helper              Spt custom 
Text Box                Txt textbox 
Timer                   Tmr timer   
Tool Bar                Tbr toolbar 
Top-level Form          Top SCX (2)         SCX form with ShowWindow = 2