DDL Event Statements

Event statements are used to define the database events for a class.

For example:

 
    class MyClass
    {
        unsigned<4> u4;
     
        event <new> newEvent;
        event <update> updateEvent;
        event <delete> deleteEvent;
        event <checkpoint> checkpointEvent;
    }
 

Database event types must be one of the following:

• new - called when an object of this class is created
• delete - called when an object of this class is deleted
• checkpoint - called when a checkpoint is called for an object of this class
• update - called when an object of this class is modified

Update events

An update event can be defined for the entire class or for a specific field of the class. The example above defines a class update event that will call the specified handler any time an existing object of this class is modified. However, if a field is specified, the specified handler will be called only when that field of an existing object is modified. For example, the following defines a field update event handler for field u4:

 
    class MyClass
    {
        unsigned<4> u4;
     
        event <u4 update> update_u4_Event;
    }
 

Note that it is not possible to define a field update event for a class that also has a class update event defined.

Events can be managed either synchronously or asynchronously. (Please refer to SDK samples 10_events_synch and 10_events_asynch for implementation details.)