Delphi in a Nutshell

Name

$IfDef Compiler Directive

Syntax

{$IfDef Name}
   ...
{$Else}
   ...
{$Endif}

Scope

Local

Description

$IfDef starts a conditional compilation section. If Name is defined (by a prior occurrence of $Define), the source code after the $IfDef directive is compiled, up to the corresponding $Else or $EndIf compiler directive. The use of $Else is optional. You can nest conditional compilation sections.

A common use for conditional compilation is to test the version of Delphi. Table 8-1 lists the symbols predefined by the compiler with the version of the compiler that defines each symbol.

Table 8-1. Predefined Symbols

Symbol	Compiler Version
CONSOLE	Defined for {$AppType Console}
CPU386	All versions
VER80	Delphi 1
VER90	Delphi 2
VER93	C++ Builder 1
VER100	Delphi 3
VER110	C++ Builder 3
VER120	Delphi 4
VER125	C++ Builder 4
VER130	Delphi 5
WINDOWS	Delphi 1
WIN32	Delphi 2, 3, 4, 5; C++ Builder 1, 3, 4

Example

{$IfOpt D+} // Debugging is enabled.
  {$define DEBUG}
  {$Assertions On}
  {$RangeChecks On}
  {$OverflowChecks On}
{$else}
  {$undef DEBUG} // Just in case it's defined in the project options
{$endif}
...
{$ifdef DEBUG}
  Log('Debug message');
{$endif}

See Also

$Define Compiler Directive, $Else Compiler Directive, $Endif Compiler Directive, $IfNDef Compiler Directive, $IfOpt Compiler Directive, $Undef Compiler Directive