Delphi Basics : $IfOpt command

DelphiBasics

$IfOpt
Compiler Directive

Tests for the state of a Compiler directive

{$IfOpt Switch-}
...
{$Else}
...
{$EndIf}

1
2	{$IfOpt Switch+} ... {$Else} ... {$EndIf}

Description

The $IfOpt compiler directive is a meta-directive - it tests for the + or - state of a single character compiler directive.

For example:

{$IfOpt H+}
ShowMessage('Longstrings are set on');
{$EndIf}

It is useful to report on directive settings at the start of a program, when testing.

Notes

$IfOpt can be used multiple times in your code.

Related commands

$Define		Defines a compiler directive symbol - as used by IfDef
$Else		Starts the alternate section of an IfDef or IfNDef
$EndIf		Terminates conditional code compilation
$IfDef		Executes code if a conditional symbol has been defined
$IfNDef		Executes code if a conditional symbol has not been defined
$UnDef		Undefines a compiler directive symbol - as used by IfDef

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Example code : Show various default directive settings

begin
  // Show the default settings of various compiler directives
  {$IfOpt A+}
    ShowMessage('Align is On');
  {$Else}
    ShowMessage('Align is Off');
  {$EndIf}

  {$IfOpt B+}
    ShowMessage('BoolEval is On');
  {$Else}
    ShowMessage('BoolEval is Off');
  {$EndIf}

  {$IfOpt H+}
    ShowMessage('LongStrings is On');
  {$Else}
    ShowMessage('LongStrings is Off');
  {$EndIf}
end;

Show full unit code

  Align is Off
  BoolEval is Off
  LongStrings is On