Release 10.1A: OpenEdge Getting Started:
Object-oriented Programming

Creating a class instance using the NEW statement

The NEW statement is used to create an instance of a class. At run time, the NEW statement locates the named class on the PROPATH using the package information in the class type name and invokes the constructor to create a new instance of the class. The instantiated class is also referred to as a class-based object. The NEW statement assigns a reference for the new class instance to an object reference variable.

This is the syntax for instantiating a class using the NEW statement:

Syntax

object-reference = NEW type-name ( [ parameter [ , parameter ] ... ] )     [ NO-ERROR ] .

Element descriptions for this syntax diagram follow:

object-reference

The name of a variable, parameter, or temp-table field appropriately defined as a class type. The class type name used in the object-reference definition must follow the rules for type-name.

Note: If object-reference is a temp-table field, its class type name can only be Progress.Lang.Object, the Progress root class. For more information on the Progress root class, see the "Using the root class — Progress.Lang.Object" section.

type-name

The type name of the class to instantiate. For more information type names, see the "Using the CLASS construct" section

This type name must also match the type name for one of the following classes involved in the class hierarchy of the class type name used to define object-reference:

The class specified in the definition of object-reference.
A class that is a subclass of the class specified in the definition of object-reference.
A class that implements the interface specified in the definition of object-reference.

[ parameter [ , parameter ] ... ]

The parameters of the constructor. For more information on the syntax of parameter, see the “Parameter passing syntax” reference entry in OpenEdge Development: Progress 4GL Reference .

Whenever an instance of a class is created, the constructor of the instantiated class, as well as the constructors of any super classes in its class hierarchy are run. The instantiated object gets its own copy of the PROTECTED and PUBLIC data members defined in the class hierarchy. Thus, just as with persistent procedures, each instance of a class is a separate entity with its own instance data.

This example, from the Main class described previously (see the "Defining an object reference as a variable" section), creates instances of two sample classes in its constructor:

CLASS Main:     DEFINE PRIVATE VARIABLE rCustObj         AS CLASS acme.myObjs.CustObj NO-UNDO.     ...     DEFINE PRIVATE VARIABLE rHelperClass         AS CLASS acme.myObjs.Common.HelperClass NO-UNDO.     CONSTRUCTOR PUBLIC Main( ):         /* Create an instance of the HelperClass class */         rHelperClass = NEW acme.myObjs.Common.HelperClass( ).         /* Create an instance of the CustObj class */         rCustObj = NEW acme.myObjs.CustObj( ).     END CONSTRUCTOR.     ... END CLASS.