How to properly make an interface support iteration?

Question

How can I expose this TList from an interface, as either IEnumerator or IEnumerator? I am using Delphi XE.

Here\'s h

Answer 1

Not an answer to your question directly (still working on that), but this is what I did to get an "interfaced enumerator", ie and interfaced class that supports iteration:

IList = interface(IInterface)
  [...]
  function GetEnumerator: TList.TEnumerator;
  function Add(const Value: T): Integer;
end;

type
  TBjmInterfacedList = class(TBjmInterfacedObject, IList)
  strict private
    FList: TList;
    function GetEnumerator: TList.TEnumerator;
  strict protected
    function Add(const Value: T): Integer;
  public
    constructor Create; override;
    destructor Destroy; override;
  end;

implementation

constructor TBjmInterfacedList.Create;
begin
  inherited;
  FList := TList.Create;
end;

destructor TBjmInterfacedList.Destroy;
begin
  FreeAndNil(FList);
  inherited;
end;

function TBjmInterfacedList.GetEnumerator: TList.TEnumerator;
begin
  Result := FList.GetEnumerator;
end;

function TBjmInterfacedList.Add(const Value: T): Integer;
begin
  Result := FList.Add(Value);
end;

And then you can do stuff like:

ISite = interface(IInterface)
  ...
end;
ISites = interface(IList);
  ...
end;

var
  for Site in Sites do begin
    ...
  end;

with implementing classes like:

TSite = class(TBjmInterfacedObject, ISite)
  ...
end;
TSites = class(TBjmInterfacedList, ISites)
  ...
end;

Update

Example project source uploaded to http://www.bjmsoftware.com/delphistuff/stackoverflow/interfacedlist.zip