Mega Code Archive
$ifdef - executes code if a conditional symbol has been defined
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{$IfDef Symbol}
... Code to run when the symbol is defined ...
{$Else}
... Code to run when the symbol is not defined ...
{$EndIf}
Description
The $IfDef compiler directive starts a section of conditionally compiled code. Only if the specified Symbol has been defined.
Symbols come in two types. Predefined in Delphi, such as Console when running a console application. And defined by the $Define compiler direcctive.
$IfDef is very useful when developing code, allowing various sections to be compiled when testing.
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
$IfNDef Executes code if a conditional symbol has not been defined
$IfOpt Tests for the state of a Compiler directive
$UnDef Undefines a compiler directive symbol - as used by IfDef
Example code : Setting up and using a test mode symbol
var
text : string;
begin
// Set our code into test mode
{$Define TESTMODE}
text := 'We are in test mode';
// Display the value of text if we are in test mode
{$IfDef TESTMODE}
ShowMessage('text = '+text);
{$EndIf}
// Switch off test mode
{$UnDef TESTMODE}
// Display the value of text if we are in test mode
{$IfDef TESTMODE}
ShowMessage('text = '+text);
{$Else}
ShowMessage('Out of test mode now');
{$EndIf}
end;
Show full unit code
We are in test mode
Out of test mode now
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