CLASS

 

Define a Class for Object Oriented Programming

Syntax

      [CREATE] CLASS <ClassName> [ <FROM, INHERIT> <SuperClass1> [,<SuperClassN>] ]  [STATIC]

Arguments

<ClassName> Name of the class to define. By tradition, Harbour classes start with “T” to avoid collisions with user- created classes.

<SuperClass1…n> The Parent class(es) to use for inheritance. Harbour supports Multiple Inheritance.

STATIC This clause causes the class function to be declared as a static function. It will therefore not be available outside the current module.

Description

CLASS creates a class from which you can create objects. The CLASS command begins the class specification, in which the DATA elements (also known as instance variables) and METHODS of the class are named. The following scoping commands may also appear. They control the default scope of DATA and METHOD commands that follow them.

         EXPORTED:
         VISIBLE:
         HIDDEN:
         PROTECTED:

    The class specification ends with the END CLASS command.

Classes can inherit from multiple <SuperClasses>, and the chain of inheritance can extend to many levels.

A program uses a Class by calling the Class Constructor, usually the New() method, to create an object. That object is usually assigned to a variable, which is used to access the DATA elements and methods.

Harbour’s OOP syntax and implementation supports Scoping (Protect, Hidden and Readonly) and Delegating, and is largely compatible with Class(y)(tm), TopClass(tm) and Visual Objects(tm).

Examples

      CREATE CLASS TBColumn

         VAR Block      // Code block to retrieve data for the column
         VAR Cargo      // User-definable variable
         VAR ColorBlock // Code block that determines color of data items
         VAR ColSep     // Column separator character
         VAR DefColor   // Array of numeric indexes into the color table
         VAR Footing    // Column footing
         VAR FootSep    // Footing separator character
         VAR Heading    // Column heading
         VAR HeadSep    // Heading separator character
         VAR Width      // Column display width
         VAR ColPos     // Temporary column position on screen

         METHOD New()    // Constructor

      ENDCLASS

Compliance

Harbour

Platforms

All

Seealso

HBClass(), Object Oriented Programming, DATA, METHOD