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1-68 SOMobjects Base Toolkit: Programmer’s Reference Manual

SOMClass Class

Description

SOMClass is the root class for all SOM metaclasses. That is, all SOM metaclasses must be

subclasses of SOMClass or some other class derived from it. It defines the essential

behavior common to all SOM classes. In particular, it provides a suite of methods for

initializing class objects, generic methods for manufacturing instances of those classes, and

methods that dynamically obtain or update information about a class and its methods at run

time.

Just as all SOM classes are expected to have SOMObject (or a class derived from

SOMObject) as their base class, all SOM classes are expected to have SOMClass or a

class derived from SOMClass as their metaclass. Metaclasses define “class” methods

(sometimes called “factory” methods or “constructors”) that manufacture objects from any

class object that is defined as an instance of the metaclass.

To define your own class methods, define your own metaclass by subclassing SOMClass or

one of its subclasses. Three methods that SOMClass inherits and overrides from

SOMObject are typically overridden by any metaclass that introduces instance

data—somInit, somUninit, and somDumpSelfInt. The new methods introduced in

SOMClass that are frequently overridden are somNew, somRenew, and somClassReady.

(See the descriptions of these methods for further information.)

Other reasons for creating a new metaclass include tracking object instances, automatic

garbage collection, interfacing to a persistent object store, or providing/managing

information that is global to a set of object instances.

File Stem

somcls

Base

SOMObject

Metaclass

SOMClass (SOMClass is the only class with itself as metaclass.)

Ancestor Classes

SOMObject

Types

typedef sequence <SOMClass> SOMClassSequence;

struct somOffsetInfo {

SOMClass cls;

long offset

};

typedef sequence <somOffsetInfo> SOMOffsets;

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