Question

I have the following code to hand enumeration over to a private field:

interface

type    

TMyClassEnumerator = class(TEnumerator<TMyClass>)
end;

TMyContainerClass = class(TObject)
private
  FItems: TObjectDictionary<string, TMyClass>;
public
  function GetEnumerator: TMyClassEnumerator;
end;

implementation

function TMyContainerClass.GetEnumerator: TMyClassEnumerator;
begin
  Result := TMyClassEnumerator(FItems.Values.GetEnumerator);
end;

Am I doing this right? I fought with implementing IENumerable<TMyClass> or creating my own interface, however, I got none of it to compile… The above code does work for example with for..in, but I feel I should make it a proper enumerable by implementing such interface.

Answer 1

Your approach is sound, but I don’t see that you need to cast, or indeed declare an enumerator class. I’d do it like this:

TMyContainerClass = class
private
  FItems: TObjectDictionary<string, TMyClass>;
public
  function GetEnumerator: TEnumerator<TMyClass>;
end;

function TMyContainerClass.GetEnumerator: TEnumerator<TMyClass>;
begin
  Result := FItems.Values.GetEnumerator;
end;