Delphi in a Nutshell

Name

Raise Keyword

Syntax

raise Object reference
raise Object reference at Pointer
raise

Description

The raise statement raises an exception. The exception object is passed to an exception handler, and Delphi will automatically free the object when the exception handler finishes. Usually, the object reference creates a new instance of an exception object, and the exception class usually inherits from the Exception class in the SysUtils unit, but you are free to raise any object reference as an exception.

By default, Delphi stores the code address of the raise statement as the exception address. You can specify a different address with the at directive.

Inside an exception handler, you can use a plain raise statement to reraise the current exception. In this case, Delphi refrains from freeing the exception object until the next exception handler in the stack gets its chance to handle the exception.

Tips and Tricks

• Low-level code and utilities should report exceptional conditions by raising exceptions. High-level and user interface code should use try-except or TApplication.OnException to catch and handle exceptions in a user-friendly manner.

• Raising and handling an exception takes time and processor resources. Do so only for exceptional conditions. Do not use exceptions as a normal way to return information. For example, a collection class might implement the Contains method to return True if the collection contains an item, and False if the item is not in the collection. The normal ...