Defined in Class.Def Inherits from AbstractClass
When you create an object, the new object's structure is determined by a template that defines how all objects of its class should be formed. This template that describes a class is an object itself. These template objects describe classes, and so are members of class Class.
Although there are a few methods that are generally useful to all programmers, most of the methods of this class are useful only for developers of system programs such as ObjectMaker. Most programmers can safely ignore most of the details of class Class.
WARNING! Some of the methods previously described in this chapter are now defined in class AbstractClass. Because class Class inherits from class AbstractClass, all these methods are available anyway. These descriptions have been moved to a new AbstractClass chapter.
Remember that if the documentation and the software (especially the definition files) disagree, always trust the software.
Class Class is a direct descendant of class AbstractClass. Class Class defines many fields that are used to specify details of the objects of the classes they represent, including the number of fields and methods defined by the class and information about its superclasses.
Unless you're creating a highly specialized tool or are extremely curious, you'll never create a class object in your packages, nor will you define one in an instance definition file. Instead, ObjectMaker will create class objects for you when you use the "define class" syntax in your object definition file.
Instantiate: rarely Subclass: rarely Call its methods: rarely
Class Class defines the following fields:
| Field | Type | Description |
|---|---|---|
| Inherited from Cited | ||
| citation | Citation | Citation for the class |
| Inherited from AbstractClass | ||
| telescriptName | ClassName | The class's telescript name |
| number | Unsigned | Index into class table |
| implSuperCount | Unsigned | Number of superclasses providing implementation |
| implSuperOffset | Unsigned | Offset to table of implementation superclasses |
| methodCount | Unsigned | Number of methods defined for class |
| methodOffset | Unsigned | Offset to table of methods |
| classFlags | Object | Miscellaneous class flags |
| Defined by Class | ||
| globalList | FieldList | List of class's globals |
| fieldList | FieldList | List of class's fields |
| instanceSize | UnsignedShort | Size of an instance |
| interfaceCount | UnsignedShort | Number of interface ancestors |
| referenceMask | Unsigned | Shows which fields are objects |
| copyReferenceMask | Unsigned | Shows which fields are copiable |
| totalCopyReferences | Unsigned | Number of copy references |
| globalData | Globals | Class's global data |
| instanceList | InstanceList | List of all instances of class |
| patchPlaces | ObjectList | List of all patch code objects |
| patchOffsets | FixedList | List of all patch code offsets |
overrides Install Call: rarely Override: sometimes
Class_Install sets up the class variables for the class. You should override Install if you want your class to initialize any global variables when the system starts up. See Object_Install for more information.
overrides Init Call: rarely Override: sometimes
When a new object is created, the system calls Init to allow the new object to set up its fields. The params parameter points to a structure that's declared like this:
typedef struct
{
ObjectID author;
ObjectID publisher;
} ClassInitParamsRec, *ClassInitParamsPtr;
Class_Init sets up fields of the new class object as follows:
| Field initialized | Initial value |
|---|---|
| instanceSize | 0 |
| totalCopyReferences | 0 |
You should override Init if your class defines any fields that should be set up to initial values when a new object is created. See Object_Init for more information.
overrides Stabilize Call: rarely Override: sometimes
When a new object is created and initialized, the object goes through a period of instability while its initial values are set up. When this unstable period is over, the system calls Stabilize to notify an object that the system won't be making frequent changes to the object.
Class_Stabilize sets the object's instanceSize field and creates a list of the class's instances. You should override Stabilize if you want to provide a way for objects of your class to convert to a tighter form, as by removing unused or obsolete data.
See Object_Stabilize for more information.
operation Expand() Call: rarely Override: rarely
The system calls Expand to convert the object to a form that might occupy more space but allows faster modification. If you've overridden Stabilize to create a tight storage format, you probably also want to override Expand. Expand should convert objects of your class to a form that makes them easier to modify.
overrides MakeGlobals() Call: rarely Override: rarely
When the class object is created, the system calls MakeGlobals to allocate space for the class variables and initialize them to zero. MakeGlobals also sets up the class object's globalData field to point to the class variables.
overrides Validate Call: rarely Override: sometimes
Class_Validate checks the following conditions and performs the following actions if the conditions are true:
| Condition | Action if true |
|---|---|
| Object has an instance list with a non-zero length | Prints debug message: instance list does not have the | name that doesn't consist of the class name | proper name | followed by " instances" |
| Instance list includes an object that's not an instance of the class | Prints debug message: (instance) is not an instance of (class), but is in the instance list |
Class_Validate calls its inherited implementation.
You should override Validate if you want objects of your class to perform any additional validity checking. See Object_Validate for more information.