Delphi - Is there a better way to get state abbreviations from state names

Question

const
states : array [0..49,0..1] of string =
(
('Alabama','AL'),
('Montana','MT'),
('Alaska','AK'),
('Nebraska','NE'),
('Arizona','AZ'),
('Nevada','NV'),
('Arkansas','AR'),
('New Hampshire','NH'),
('California','CA'),
('New Jersey','NJ'),
('Colorado','CO'),
('New Mexico','NM'),
('Connecticut','CT'),
('New York','NY'),
('Delaware','DE'),
('North Carolina','NC'),
('Florida','FL'),
('North Dakota','ND'),
('Georgia','GA'),
('Ohio','OH'),
('Hawaii','HI'),
('Oklahoma','OK'),
('Idaho','ID'),
('Oregon','OR'),
('Illinois','IL'),
('Pennsylvania','PA'),
('Indiana','IN'),
('Rhode Island','RI'),
('Iowa','IA'),
('South Carolin','SC'),
('Kansas','KS'),
('South Dakota','SD'),
('Kentucky','KY'),
('Tennessee','TN'),
('Louisiana','LA'),
('Texas','TX'),
('Maine','ME'),
('Utah','UT'),
('Maryland','MD'),
('Vermont','VT'),
('Massachusetts','MA'),
('Virginia','VA'),
('Michigan','MI'),
('Washington','WA'),
('Minnesota','MN'),
('West Virginia','WV'),
('Mississippi','MS'),
('Wisconsin','WI'),
('Missouri','MO'),
('Wyoming','WY')
);
function getabb(state:string):string;
var
  I:integer;
begin
  for I := 0 to length(states) -1 do
  if lowercase(state) = lowercase(states[I,0]) then
  begin
    result:= states[I,1];
  end;
end;
function getstate(state:string):string;
var
  I:integer;
begin
  for I := 0 to length(states) -1 do
  if lowercase(state) = lowercase(states[I,1]) then
  begin
    result:= states[I,0];
  end;
end;
procedure TForm2.Button1Click(Sender: TObject);
begin
 edit1.Text:=getabb(edit1.Text);
end;

procedure TForm2.Button2Click(Sender: TObject);
begin
 edit1.Text:=getstate(edit1.Text);
end;

end.

Is there a bette way to do this?

Answer 1

If you're on D2009 or D2010, use a TDictionary<string, string> from Generics.Collections. Declare the array of constants like you have it, then set up your dictionary by putting each pair in to the dictionary. Then just use the dictionary's default property to do your lookups.

Answer 2

Notice that lowercase(a) = lowercase(b) is slower than sameText(a, b).

In addition, you can speed up the procedure further by storing the strings in the array as lower-case only, and then in the look-up routine start with converting the input to lower-case as well. Then you can use the even faster function sameStr(a, b). But of course, when a match is found, you then need to format it by capitalizing the initial letters. This speed-up approach is probably not very important for such a small list of strings. After all, there are not too many states in the US.

Also, you should declare the functions using const arguments, i.e. write

function getabb(const state:string):string;

instead of

function getabb(state:string):string;

(unless you want to change state in the routine).

Finally, you could make the code more compact and readable by omitting the begin and end of the for loops.

Answer 3

Should this kind of data be hard coded?
Wouldn't it be better to use something like a XML file or even just a CSV.

Or Name Value Pairs, i.e. IA=Iowa
then loaded into a TStringList to get

States.Values['IA'] = 'Iowa';

Then you just need to write something to search the Values to work backwards like

//***Untested***
//Use: NameOfValue(States, 'Iowa') = 'IA'

function NameOfValue(const strings: TStrings; const Value: string): string;
var
  i : integer;
  P: Integer;
  S: string;
begin
  for i := 0 to strings.count - 1 do
  begin
    S := strings.ValueFromIndex[i];
    P := AnsiPos(strings.NameValueSeparator, S);
    if (P <> 0) and (AnsiCompareText(Copy(S, 1, P - 1), Value) = 0) then
     begin
      Result := strings.Names[i];
      Exit;
     end;
  end;
  Result := '';
end;

I'm fairly sure its case insensitive too

Answer 4

I would have your lists sorted. That way you can use a binary search to cut the lookup times down. It all depends on the number of iterations you will be exercising. Around 50 items doesn't seem like much, until your iterating over the list a few thousand times looking for the last item in the list.

Also you should ALWAYS bail from your loops as soon as you get get a match if you know the rest of the list will not match.

Arrays are fine, and depending on how your using the data, you might need to add some of the "territories" that also have abbreviations (PR = PUERTO RICO, GU = GUAM, etc.).