Delphi open array as property index in indexed property

Question

Is it possible to use an open array as index type for indexed properties?

unit OpenArrayAsPropertyIndex;

interface

type

  TFoo = class
  private
    function getBar(Index: array of Integer): String;
  public
    // [DCC Error]: E2008 Incompatible types
    property Bar[Index: array of Integer]: String read getBar;
  end;

implementation

function TFoo.getBar(Index: array of Integer): String;
begin

end;

end.

The property getter is generated by pressing Ctl+Shift+C in the IDE, but this code doesn't compile and gives error "E2008 Incompatible types". So, is it a language limitation, or what is the correct parameter signature for the getter?

Counter question: how should the code look to use such a property? Do you have an answer for this? — AmigoJack
– AmigoJack, Commented Dec 15, 2021 at 13:44
@Uli Gerhardt: "const" doesn't work, it gives the same error. — malom
– malom, Commented Dec 15, 2021 at 13:51
@AmigoJack: I'm just playing. But obviously it should be used as "s := Foo.Bar[[1,2,3]];" — malom
– malom, Commented Dec 15, 2021 at 13:57

Uwe Raabe · Accepted Answer · 2021-12-15 13:57:52Z

1

Instead of array of Integer use TIntegerDynArray from System.Types or a similar self declared type.

type
  TIntArray = array of Integer;
  TFoo = class
  private
    function getBar(Index: TIntArray): String;
  public
    property Bar[Index: TIntArray]: String read getBar;
  end;

function TFoo.getBar(Index: TIntArray): String;
begin

end;

answered Dec 15, 2021 at 13:57

Uwe Raabe

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3 Comments

David Heffernan Over a year ago

TArray<Integer>

Uli Gerhardt Over a year ago

But this is a dynamic array, not an open array. (Which might be fine for the OP, considering his comment above.)

Uwe Raabe Over a year ago

Open arrays are only allowed as parameters of procedures et al. Most likely that doesn't include indexed properties. It depends on the intended use if my answer is valid.

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