DN4DP#13: Overloaded default array properties

It's been a while now, but this post continues the series of The Delphi Language Chapter teasers from Jon Shemitz’ .NET 2.0 for Delphi Programmers book.

What a good time to continue this series just after the major Delphi for .NET 2.0 launch, CodeGear RAD Studio 2007!

The previous post covered the exotic topic of Record Helpers. Today we'll look at another exotic-ish topic - overloaded default array properties.

Note that I do not get any royalties from the book and I highly recommend that you get your own copy – for instance at Amazon.

"Overloaded default array properties

A class or component can have an array property that is declared as default. This mechanism has now been extended to allow multiple overloaded default array properties - as long as the number or types of indexer parameters are different.

type
  TMyObject = class
  public
    property Items[Index: integer]: string read GetItems write SetItems; default;
    property Items[const Name: string]: string read GetNamedItems write SetNamedItems; default;
  end;

This means that you can use the array indexing syntax on the object instance - effectively overloading the array subscript operator [].

procedure Test; 
var 
  MyObject: TMyObject; 
begin 
  MyObject := TMyObject.Create; 
  MyObject[42] := 'The Answer'; 
  MyObject['Bar'] := 'Yes'; 
end; 

"