How to convert classname as string to a class?

Question

I have classnames in a stringlist. For example it could be \'TPlanEvent\', \'TParcel\', \'TCountry\' etc.

Now I want to find out the sizes by looping the list.

Answer 1

In Delphi 2010 you can use:

function StringToClass(AName: string): TClass;
var
  LCtx: TRttiContext;
  LTp: TRttiType;
begin
  Result := nil;

  try
    LTp := LCtx.FindType(AClassName);
  except
    Exit;
  end;

  if (LTp <> nil) and (LTp is TRttiInstanceType) then
    Result := TRttiInstanceType(LTp).Metaclass;
end;

One note. Since you only keep the class names in the list this method will not work because TRttiContext.FindType expects a fully qualified type name (ex. uMyUnit.TMyClass). The fix is to attach the unit where you store these classes in the loop or in the list.