Using an enum with generics

Question

I\'m trying to create a generic class to which I can use a set of enums to initiate the values inside. For example:

constructor TManager.Create         


        

Answer 1

As David mentioned the best you can do is at runtime with RTTI.

    type  
      TRttiHelp = record
        class procedure EnumIter; static;
      end;

    class procedure TRttiHelp.EnumIter;
    var
      typeInf: PTypeInfo;
      typeData: PTypeData;
      iterValue: Integer;
    begin
      typeInf := PTypeInfo(TypeInfo(TEnum));
      if typeInf^.Kind <> tkEnumeration then
        raise EInvalidCast.CreateRes(@SInvalidCast);

      typeData := GetTypeData(typeInf);
      for iterValue := typeData.MinValue to typeData.MaxValue do
        WhateverYouWish;
    end;  

Although I don't know how the code behaves when your enum has defined values such as

    (a=9, b=19, c=25)

---

Edit:

If you would like to return iterValue to the enum, you may use the following function, taken from a enum helper class by Jim Ferguson

class function TRttiHelp.EnumValue(const aValue: Integer): TEnum;
var
  typeInf: PTypeInfo;
begin
  typeInf := PTypeInfo(TypeInfo(TEnum));
  if typeInf^.Kind <> tkEnumeration then
    raise EInvalidCast.CreateRes(@SInvalidCast);

  case GetTypeData(typeInf)^.OrdType of
    otUByte, otSByte:
      PByte(@Result)^ := aValue;
    otUWord, otSWord:
      PWord(@Result)^ := aValue;
    otULong, otSLong:
      PInteger(@Result)^ := aValue;
  else
    raise EInvalidCast.CreateRes(@SInvalidCast);
  end;
end;

You may then use the generically provided as the index to the dictionary in your constructor.