Delphi in a Nutshell

Name

Assigned Function

Syntax

function Assigned(P: Pointer): Boolean;
function Assigned(Obj: TObject): Boolean;
function Assigned(Method: TMethod): Boolean;

Description

The Assigned function returns True if the argument is not nil; it returns False if the argument is nil. Assigned is not a real function.

Tips and Tricks

• The argument can be a pointer, an object reference, or a method.

• Calling Assigned instead of comparing a pointer with nil incurs no performance penalty.

• If the pointer is a function pointer, using Assigned makes it clear that you do not intend to call the function and compare its result to nil. Thus, Assigned is often used to test function and method pointers.

• A method pointer has two parts: a code pointer and a data pointer. Assigned checks only the most significant word of the code reference: if the high-order word is zero, the method reference is nil. Assigned ignores the data pointer.

See Also

Nil Keyword