Determining if an object is a subclass

It can sometimes be useful to determine if an object is a instance of a subclass of some specified parent class.

While over-use of this probably suggests a class framework which has not been well designed, it is valuable in specific instances.

There are two static methods on the SysDictClass which can be used for this purpose: <xpp> static boolean isSuperclass(classId _id, classId _potentialAncestorId) </xpp> This method checks if the classId passed in _id is a subclass of the _potentialAncestorId

<xpp> static boolean isEqualOrSuperclass(classId _id, classId _potentialAncestorId) </xpp>

This method checks if the classId passed in _id is a subclass of the _potentialAncestorId, and will also return true if _id equals _potentialAncestorId

The following code uses the SalesTableType heirarchy as an example.

<xpp> SalesTableType stt; SalesTableType_Journal stt_j;

// This is true as stt is an instance of SalesTableType if (SysDictClass::isEqualOrSuperclass(classidget(stt), classnum(SalesTableType))) {

   // Code here will be run

}

// This is true as stt_j is a subclass of SalesTableType if (SysDictClass::isEqualOrSuperclass(classidget(stt_j), classnum(SalesTableType))) {

   // Code here will be run

}

// This is true as stt_j is an instance of SalesTableType_Journal if (SysDictClass::isEqualOrSuperclass(classidget(stt_j), classnum(SalesTableType_Journal))) {

   // Code here will be run

}

// This is FALSE as stt is NOT an instance or subclass of SalesTableType_Journal if (SysDictClass::isEqualOrSuperclass(classidget(stt), classnum(SalesTableType_Journal))) {

   // Code here will NOT be run

} </xpp>