CLASS entries (also referred to simply
as
classes) store the definitions of components
that can be used to build FRAME entries. You use the BUILD procedure's
Class Editor window to edit the component definitions in CLASS entries.
Changing the properties
of a class changes the properties of all instances of the class and
of any subclasses that are derived from the class.
The class definition
in a CLASS entry consists of the following elements:
Description
is a description for
the CLASS entry that is also used as the name for the class when it
appears in the Components window for use in building FRAME entries.
Parent Class
specifies the four-level
name of the CLASS entry from which the current class inherits its
attributes, methods, events, event handlers, and interfaces. Once
you specify the parent class for a new class, you cannot change it.
Meta Class
specifies the optional
four-level name of a CLASS entry of which the current class is an
instance. The metaclass enables you to collect information about and
modify the behavior of the current class at run time. The metaclass
also enables the current class to obtain information about parent
classes and child classes.
By default, all classes
are instances of the Class metaclass. See the description of the Class
class in the online Help for
SAS/AF software for more information
about the methods that the default metaclass provides.
Class Properties
define the appearance
and behavior of the class. In the SAS Component Object Model (SCOM),
classes have the following properties:
Attributes
define characteristics
of the component, such as its name, description, color, label, or
size. Each attribute specification consists of a list of metadata
that includes the attribute name, value, type, scope, description,
and other items that enable functionality.
Methods
define the operations
that can be executed by any component you create from the class. Each
method specification consists of a list of metadata that includes
the method name, signature, description, and the name and label of
the entry that contains the method implementation. A method's signature
is comprised of the method's arguments and their types and order;
it uniquely identifies the method to the SCL compiler.
The code that implements
the method is not stored in the CLASS entry itself, but rather in
an entry specified in the metadata. The implementation typically consists
of a labeled CLASS, USECLASS, or METHOD section in an SCL entry.
Events
alert applications
when there is a change of state, such as when the user clicks the
mouse button on a component that was created from the class. Each
event specification consists of a list of metadata that includes the
event name, description, and items that determine whether the event
is enabled and how it is sent.
Event handlers
specify which methods
are executed after events occur. Each event handler specification
consists of an list of metadata that includes the name of the event
that is handled, the name of the object that generates the event,
the name of the method to execute in response to the event, and a
description.
Interfaces
enable components that
you create from the class to indirectly call methods in another component.
Each interface specification includes the name of the INTRFACE entry
that contains the interface definition. Refer to
INTRFACE Entries for more information.
Refer to the online
Help for
SAS/AF software for details about the attributes, methods,
events, event handlers, and interfaces of the classes that are provided
with
SAS/AF software.
You can use RESOURCE
entries to collect individual classes into libraries. Doing this simplifies
the maintenance and deployment of the classes. See
RESOURCE Entries for more information.
For an introduction
to using classes and creating your own CLASS entries, refer to the
Guide to SAS/AF Applications Development or the
Getting Started with SAS/AF and Frames.