Event-handling mechanisms

An event-handling mechanism provides a way for one DataBlade® API module to inform another module (or another part of the same module) that an event has occurred during execution of a function.

An event-handling mechanism has two parts:
  • A function that throws an event

    A function in a DataBlade® API module might encounter a condition that it cannot handle. Events represent many common conditions (see DataBlade API event types). When a module encounters one of these conditions, it can throw the associated event to indicate that some event handling needs to be performed.

  • A function that catches an event

    A special function, called a callback function, is invoked when its associated event occurs. The callback function can perform the appropriate actions to handle or recover from this event.

This division of event-handling responsibility enables you to put common event-handling code for a particular condition in a single location, in a callback function. Any DataBlade® API module that requires the associated event handling can then register this callback function.

When an event occurs, the DataBlade® API performs event handling based on whether it finds a registered callback that can catch (or handle) the event, as follows:
  • If a registered callback exists for the event, the DataBlade® API invokes this callback.
  • If no registered callback exists for the event, the DataBlade® API takes the appropriate default behavior.