More precisely, we are subclassing a Visual Foxpro base class. These statements create new classes based on Visual Foxpro’s built-in classes. When creating new classes, we use the new DEFINE CLASS command: Just be sure to place the CREATEOBJECT() function calls before any class definitions! The code that follows can be typed directly into a PRG. While it’s possible and probably more desirable to create all your classes, including non-visual ones, using the Class Designer, it’s easier and more straightforward in a chapter of this nature to demonstrate the features of the language in code. Invoked when an error occurs inside one of the object’s methods You can place code in a command button’s Click() event method that will automatically run whenever the button is clicked.Īll Visual Foxpro base classes can respond to a common minimum set of events: Event For example, when the user clicks on a command button, Visual Foxpro invokes the Click event.

In Visual Foxpro, object can also respond to events that occur in the system. Most objects also exhibit some kind of behavior in the form of methods. You are free to add custom properties to any new class you create. The name of the class of the parent class of the object The full path of the class library where this class is defined All Visual Foxpro base classes share a common minimum set of properties: Property Here is the current list of base classes:Īn object has properties used to describe the object, or to hold values that represent the object’s state. The form is referred to as the Parent, while the text boxes are referred to as children (or child controls). A good example of a container is a form that contains a group of text boxes. (The “control” control is somewhat of an exception to this rule, since it allows us to refer to multiple controls as if they were one).

The difference is that a container can include other controls or even other containers within itself, while a control cannot. These built-in classes are called base classes.īase classes are grouped into controls and containers. The model includes a set of built-in classes that you use as a basis for creating your own classes. User defined classes, protected class members, inheritance, - everything you would expect to find in a robust object model. The Visual Foxpro object model is based on a strong foundation of object-oriented principles. Alan Griver, ISBN 0-7821-1648-5, Copyright ©1995 SYBEX Inc.,by permission of SYBEX Inc. This article is excerpted from The Visual FoxPro® 3 Codebook by Y.

Vfp define class