type
  TMyType = (mtFirst, mtSecond, mtThird);

unit Enumerator;
 
interface
 
uses
  System.TypInfo, System.Math;
 
type
  TEnumeration<T> = class
  strict private
    class function TypeInfo: PTypeInfo; inline; static;
    class function TypeData: PTypeData; inline; static;
  public
    class function IsEnumeration: Boolean; static;
    class function ToOrdinal(Enum: T): Integer; inline; static;
    class function FromOrdinal(Value: Integer): T; inline; static;
    class function MinValue: Integer; inline; static;
    class function MaxValue: Integer; inline; static;
    class function InRange(Value: Integer): Boolean; inline; static;
    class function EnsureRange(Value: Integer): Integer; inline; static;
  end;
 
implementation
 
class function TEnumeration<T>.TypeInfo: PTypeInfo;
begin
  Result := System.TypeInfo(T);
end;
 
class function TEnumeration<T>.TypeData: PTypeData;
begin
  Result := System.TypInfo.GetTypeData(TypeInfo);
end;
 
class function TEnumeration<T>.IsEnumeration: Boolean;
begin
  Result := TypeInfo.Kind = tkEnumeration;
end;
 
class function TEnumeration<T>.ToOrdinal(Enum: T): Integer;
begin
  Assert(IsEnumeration);
  Assert(SizeOf(Enum) <= SizeOf(Result));
  Result := 0;
  Move(Enum, Result, SizeOf(Enum));
  Assert(InRange(Result));
end;
 
class function TEnumeration<T>.FromOrdinal(Value: Integer): T;
begin
  Assert(IsEnumeration);
  Assert(InRange(Value));
  Assert(SizeOf(Result) <= SizeOf(Value));
  Move(Value, Result, SizeOf(Result));
end;
 
class function TEnumeration<T>.MinValue: Integer;
begin
  Assert(IsEnumeration);
  Result := TypeData.MinValue;
end;
 
class function TEnumeration<T>.MaxValue: Integer;
begin
  Assert(IsEnumeration);
  Result := TypeData.MaxValue;
end;
 
class function TEnumeration<T>.InRange(Value: Integer): Boolean;
var
  ptd: PTypeData;
begin
  Assert(IsEnumeration);
  ptd := TypeData;
  Result := System.Math.InRange(Value, ptd.MinValue, ptd.MaxValue);
end;
 
class function TEnumeration<T>.EnsureRange(Value: Integer): Integer;
var
  ptd: PTypeData;
begin
  Assert(IsEnumeration);
  ptd := TypeData;
  Result := System.Math.EnsureRange(Value, ptd.MinValue, ptd.MaxValue);
end;
 
end.

myTypeselection := TEnumeration<TMyType>.FromOrdinal(MyRadiogroup.ItemIndex);