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:

static boolean isSuperclass(classId  _id, classId  _potentialAncestorId)

This method checks if the classId passed in _id is a subclass of the _potentialAncestorId

static boolean isEqualOrSuperclass(classId  _id, classId  _potentialAncestorId)

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.

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

}