Delphi in a Nutshell

Name

Index Directive

Syntax

function Getter(Index: Integer): Property type;
procedure Setter(Index: Integer; Value: Property type);
property Name: Property type index Constant read Getter write Setter;

function ArrayGet(Index: Integer; ArrayIndex: Index type): Prop. type;
procedure ArraySet(Index: Integer; ArrayIndex: Index type;
  Value: Property type);
property Name[ArrayIndex: Index type]: Property type index Constant
  read Getter write Setter;

exports
  Subroutine index Constant;

Subroutine header; external DllName index Constant;

Description

The index directive has three distinct uses: declaring indexed properties, exporting subroutines, and importing subroutines.

• Multiple properties can reuse a getter or setter method by specifying an index directive and a unique index value. The index value is passed as the first argument to the getter and setter methods. See the property keyword for more information.

• A unit or library can export subroutines with the exports declaration. Every exported subroutine has a unique index. If you do not supply an index directive, Delphi automatically assigns a unique index. See the exports keyword for more information.

• A subroutine declaration can use the external directive to import a subroutine from a DLL. By default, Delphi looks up the subroutine by name. If you supply an index directive, Delphi looks up the subroutine by index number, which is slightly faster (but subject to the possibility that the index number will change in a future revision of the ...