What “type of” declaration represents in Delphi and how can it be used

Question

There is some strange code in Datasnap.DSReflect unit

  TDSAdapterClassType = type of TDSAdapterClass;

  TDSAdapterClass = class(TPersistent)
  pri         


        

Answer 1

In Delphi.Net we have the following definitions in SysUtils:

type
  TInterfaceRef = type of interface;

  function Supports(const Instance: TObject; const IID: TInterfaceRef): Boolean; overload; inline;

So it was some kind of replacement for class of that can be used for interface types.

The following document mentions a "Type reference syntax (type of Interface)": http://edn.embarcadero.com/article/29780

Here's some more info: http://hallvards.blogspot.de/2004/11/object-to-interface-casts.html