You can compare two object references for equality using the equals operator (=), which checks if two object references are actually referencing the same object. The object references can be equal even if the object references have been defined for different classes in the class hierarchy. If the two object references are defined for different classes, they are also equal if they are both set to the Unknown value (?).

Note: You can also perform the same object reference comparison using the Equals( ) method on Progress.Lang.Object. For more information, see Use the root class: Progress.Lang.Object.

The following example demonstrates the use of the equal operator using the two object references stored in rSuper and rSubClass:

VAR SubClass rSubClass = NEW SubClass( ).
VAR SuperClass rSuper.

rSuper = rSubClass.

IF rSuper = rSubClass THEN
  MESSAGE "they are the same".

The MESSAGE statement will indeed be executed, demonstrating that rSuper and rSubClass are equal even though they reference different class types in the class hierarchy.