Enumeration inheritance delphi

Something similar is possible in the reverse order. If you know all the possible values, define it as a base type and declare subrange types of it. The subranges will be assignement compatible with the base type and with each other. It may or may not be a benefit.

type
 TEnumAll = (enFirst, enSecond, enThird, enFourth, enFifth);
 TEnumLower = enFirst..enThird;
 TEnumMore = enFirst..enFourth;
procedure TForm1.Test1;
var
  All: TEnumAll;
  Lower: TEnumLower;
begin
  for All := Low(TEnumAll) to High(TEnumAll) do begin
   Lower := All;
  end;
  for Lower := Low(TEnumLower) to High(TEnumLower) do begin
    All := Lower;
  end;
end;

It can be done with an trick, using Include files. Example:

AdCommonAttributes.inc

canonicalName,
cn,
whenCreated,
description,
displayName,
distinguishedName,
instanceType,
memberOf,
modifyTimeStamp,
name,
objectCategory,
objectClass,
objectGuid,
showInAdvancedViewOnly

AdUserGroupCommonAttributes.inc:

msDSPrincipalName,
objectSid,
sAMAccountName

AdUserAttributers.inc:

accountExpires,
badPasswordTime,
badPwdCount,
c,
comment,
company,
department,
division,
employeeID,
givenName,
homeDirectory,
homeDrive,
lastLogon,
lockoutTime,
logonCount,
pwdLastSet,
sn,
telephoneNumber,
tokenGroups,
userAccountControl,
userPrincipalName

unit AdUserGroupCommonAttributes;

   TAdUserGroupCommonAttributes = (
    {$I AdCommonAttribs.inc}, {$I AdUserGroupCommonAttributes.inc}
   );

unit AdGroupAttributes;

type
  TAdGroupAttributes = (
    {$I AdCommonAttribs.inc},
    {$I AdUserGroupCommonAttributes.inc},
    {$I AdGroupAttributes.inc}
  );

unit AdUserAttributes;

type
  TAdUserAttributes = (
    {$I AdCommonAttribs.inc},
    {$I AdUserGroupCommonAttributes.inc},
    {$I AdUserAttributes.inc}
  );

This is not possible because the enumerated names should be unique. You cannot use the values of TTypeKind in another enumeration, it generates conflict.

However in Delphi 2009 there is a feature called scoped enums. You can say TMyTypeKind.enBoolean.

But this does not solve the inheritance.

One way is to assign integer constants to the enum values:

Type TMyTypeKind = (enBoolean = High(TTypeKind) + 1, enPath = High(TTypeKind) + 2);

So you can have an index number that begins in Low(TTypeKind) and ends in High(TMyTypeKind)

See it for yourself: Ord(enBoolean)

I am afraid this is not possible at all. Theres nothing you can do about it, I am sorry,

When you type:

Type TMyTypeKind = (TTypeKind, enBoolean, enPath);

Delphi will see that TTypeKind is already a type and it will give you the follow error:

[DCC Error] xxx.pas(41): E2004 Identifier redeclared: 'TTypeKind'

As it was already said, you can't. But you may do this way:

TBaseState = class
  public const
    stNone = 1;
    stSingle = 2;
  end;

  TMyState = class(TBaseState)
  public const
    stNewState = 3;
  end;

  var
    state: TMyState;

  begin
    ShowMessage(IntToStr(s.stNewState));
  end;

It isn't the same with enums, but sometimes it helps.