Iterate through items in an enumeration in Delphi

Question

I want to iterate through the items in an enumeration.

I'd like to be able to say something like this:

type
  TWeekdays = (wdMonday, wdTuesday, wdWednesday, wdThursday, wdFriday);

...
elementCount := GetElementCount(TypeInfo(TWeekDays));

for i := 0 to elementCount - 1 do begin
  ShowMessage(GetEnumName(TypeInfo(TWeekdays),i));
end;

The closest I've been able to come is this:

function MaxEnum(EnumInfo: PTypeInfo): integer;
const
  c_MaxInt = 9999999;
var
  i: integer;
  s: string;
begin
  //get # of enum elements by looping thru the names
  //until we get to the end.
  for i := 0 to c_MaxInt do begin
    s := Trim(GetEnumName(EnumInfo,i));
    if 0 = Length(s) then begin
      Result := i-1;
      Break;
    end;
  end;
end;

Which I use like this:

procedure TForm1.BitBtn1Click(Sender: TObject);
var
  i, nMax: integer;
begin
  ListBox1.Clear;
  nMax := MaxEnum(TypeInfo(TWeekdays));
  for i := 0 to nMax do begin
    ListBox1.Items.Add(GetEnumName(TypeInfo(TWeekdays),i));
  end;
end;

That works well, except the list I get looks like this (notice the last two items):

wdMonday
wdTuesday
wdWednesday
wdThursday
wdFriday
Unit1
'@'#0'ôÑE'#0#0#0#0#0#0#0#0#0#0#0#0#0

The two items at the end are obviously not what I want.

Is there a better way to iterate through the elements of an enumerated type?

If not, then is it safe to assume that there will always be exactly two extra items using my current method? Obviously one is the Unit name... but what is the "@" symbol doing? Is it really garbage, or is it more type information?

I'm using Delphi 2007. Thanks for any insights.

user_46207 · Answer

This example compiles on Delphi Sydney (10.4)

 type
   TDay = (Mon=1, Tue, Wed, Thu, Fri, Sat, Sun);   // Enumeration values
 var
   day   : TDay;          // Enumeration variable
 begin
   for day := Mon to Fri do
      Caption:= IntToStr(ord(day));
 end;

( http://www.delphibasics.co.uk/Article.asp?Name=Sets )

Iterate through items in an enumeration in Delphi

5 Answers