Subscribes an event handler method or procedure to an ABL or .NET class event.
Return type: VOID
Access: PUBLIC
Applies to: ABL or .NET class events
Syntax
[ publisher : ] event-name:Subscribe
( [ subscriber : ] handler-method ) [ NO-ERROR ]
|
[ publisher : ] event-name:Subscribe
( [ subscriber-handle , ] handler-procedure ) [ NO-ERROR ]
|
- [
publisher : ]
- The object reference to an ABL or .NET object or the type name of an
ABL or .NET class that can publish the instance or static event, respectively. If you do
not specify a publisher, it defaults to either
THIS-OBJECT when event-name
identifies an instance event defined in the current class instance, or to the class type
name of the current class definition when event-name
identifies a static event defined in the current class hierarchy.
-
event-name
- The name of an ABL or .NET event that publisher can
publish. At compile time, ABL verifies that event-name is
an accessible member of the class referenced by publisher.
The event can be an abstract event.
- [
subscriber : ]
handler-method
- An ABL class-based method that you want to subscribe as a handler for
event-name, where handler-method is the unquoted name of a pure ABL instance or static
method. If specified, subscriber can be either the
object reference to an ABL class instance where handler-method is defined, or the type name of an ABL class where the
static handler-method is defined. If you do not
specify a subscriber, it defaults to either
THIS-OBJECT when handler-method
identifies an instance method defined in the current class hierarchy, or to the class
type name of the current class definition when handler-method identifies a static method defined in the current class
hierarchy.
Note: The specified handler-method cannot be a .NET method.
Note
that the access mode (PUBLIC, PROTECTED, or PRIVATE) of the handler-method definition does not matter to the publisher. For example, you can subscribe a PRIVATE method of the
subscribing class instance as a handler to an event defined and published by yet
another class instance.
The signature of handler-method does not have to be identical with the
signature defined for event-name, but it must be run-time
compatible. This includes an overloaded method as long as ABL can identify the
signature for a unique overloading that is compatible with the event signature.
Thus, ABL raises a compile-time error if handler-method:
- Is not accessible to the context where this Subscribe( ) method executes
- Does not have a run-time compatible signature
- Does not have a unique overloading that is compatible with the
event signature
- [
subscriber-handle , ]
handler-procedure
- A procedure that you want to subscribe as a handler for event-name, where handler-procedure is a character expression that evaluates to the name of
an internal procedure. If specified, subscriber-handle is a handle to a persistent procedure, or any other
external procedure on the call stack, where the internal procedure is defined.
Otherwise, subscriber-handle defaults to
THIS-PROCEDURE.
At compile-time, ABL checks this
Subscribe( ) method call only to verify that any
specified subscriber-handle is a HANDLE data type
and that handler-procedure is specified by a
character expression. Otherwise, the AVM raises a run-time error if the procedure
context specified by subscriber-handle is not
accessible or it does not define handler-procedure
as an internal procedure.
- NO-ERROR
- The NO-ERROR option is used to
prevent the statement from raising ERROR and
displaying error messages.
