Chapter 2: System Object Properties, Events, and Functions

RuntimeError object

The RuntimeError object inherits from the Throwable object and is used by the PocketBuilder virtual machine (PBVM) to throw runtime errors. Runtime errors are also called unchecked exceptions. You do not need to declare where they might be thrown and you do not need to catch them as you do checked exceptions.

When a RuntimeError is thrown, its properties are populated automatically with the runtime information associated with the line where the error occurred. If a RuntimeError is not handled, the Application object SystemError event is triggered and the global Error object is populated with the runtime information.

The following derived types provide more robust error-handling capabilities:

DivideByZeroError – thrown when an attempt is made to divide by zero.
NullObjectError – thrown when an attempt is made to access an object using a null reference.
DWRuntimeError – thrown when a DataWindow error occurs that is not handled by an Error event script.

The descendants of RuntimeError allow you to handle specific runtime errors. For example, you could catch only NullObjectError exceptions in a specific block of code. Alternatively, you can catch all runtime errors with a single CATCH statement.

Properties

RuntimeError property	Datatype	Description
ClassDefinition	PowerObject	An object of type PowerObject containing information about the class definition of the object or control
Class	String	Name of the class where the exception occurred
DLLName	String	(PBXRuntimeError only) Name of the PocketBuilder extension DLL where the exception occurred
Line	Integer	Line number where the exception occurred
Number	Integer	Identifies the PocketBuilder error
ObjectName	String	Name of the object where the exception occurred
RoutineName	String	Name of the event or routine where the exception occurred
Text	String	Text associated with the type of exception

Events

RuntimeError event	Occurs
Constructor	When the exception is thrown
Destructor	Immediately after the exception is thrown

Functions

RuntimeError function	Datatype returned	Description
ClassName	String	Returns the name assigned to the object.
GetContextService	Integer	Creates a reference to a context-specific instance of the specified service.
GetMessage	String	Returns the error message from objects of type Throwable.
GetParent	PowerObject	Returns a reference to the name of the parent object.
PostEvent	Boolean	Adds an event to the end of the message queue for the object.
SetMessage	—	Sets an error message for an object of type Throwable.
TriggerEvent	Integer	Triggers a specific event in the object and executes the script for the event.
TypeOf	Object	Returns the type of the object.

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