Best way to find if a string is in a list (without generics)

Question

I want do something like this:

Result = 'MyString' in [string1, string2, string3, string4];

This can't be used with strings and I don't want to do something like this:

Result = (('MyString' = string1) or ('MyString' = string2));

Also I think that creating a StringList to do just this is too complex.

Is there some other way to achieve this?

Thanks.

score 70 · Accepted Answer · edited Jul 30 '20 at 06:58

70

You could use AnsiIndexText(const AnsiString AText, const array of string AValues):integer or MatchStr(const AText: string; const AValues: array of string): Boolean; (Both from StrUtils unit)

Something like:

Result := (AnsiIndexText('Hi',['Hello','Hi','Foo','Bar']) > -1);

or

Result := MatchStr('Hi', ['foo', 'Bar']);

AnsiIndexText returns the 0-offset index of the first string it finds in AValues that matches AText case-insensitively. If the string specified by AText does not have a (possibly case-insensitive) match in AValues, AnsiIndexText returns –1. Comparisons are based on the current system locale.

MatchStr determines if any of the strings in the array AValues match the string specified by AText using a case sensitive comparison. It returns true if at least one of the strings in the array match, or false if none of the strings match.

Note AnsiIndexText has case-insensitively and MatchStr is case sensitive so I guess it depends on your use

EDIT: 2011-09-3: Just found this answer and thought I would add a note that, in Delphi 2010 there is also a MatchText function which is the same as MatchStr but case insenstive. -- Larry

edited Jul 30 '20 at 06:58

Fabrizio

7,603
6
44
104

answered Oct 29 '08 at 13:15

Re0sless

10,678
6
51
66

Actually there is a better one, just searched a little in the StrUtils.pas and found the MatchStr which returns a Boolean: Result := MatchStr('Hi', ['foo', 'Bar']); Please add it to your answer. – Fabio Gomes Oct 29 '08 at 13:48
MatchStr and MatchText are also available in Delphi 2007. – Jerry Gagnon Oct 03 '11 at 15:04
any equivalent for delphi 7 ? – CyprUS May 03 '12 at 11:26
1

@JerryGagnon: In which unit? I can't find them in `SysUtils` – Fabrizio Feb 26 '19 at 16:55
1

@Fabrizio they are in `StrUtils` – Re0sless Feb 27 '19 at 12:38

score 9 · Answer 2 · edited Oct 31 '08 at 23:26

9

The code by Burkhard works, but iterates needlessly over the list even if a match is found.

Better approach:

function StringInArray(const Value: string; Strings: array of string): Boolean;
var I: Integer;
begin
  Result := True;
  for I := Low(Strings) to High(Strings) do
    if Strings[i] = Value then Exit;
  Result := False;
end;

edited Oct 31 '08 at 23:26

Jim McKeeth

38,225
23
120
194

answered Oct 29 '08 at 13:10

gabr

26,580
9
75
141

Burkhard · Answer 3 · 2008-10-29T13:02:38.810

2

Here is a function that does the job:

function StringInArray(Value: string; Strings: array of string): Boolean;
var I: Integer;
begin
  Result := False;
  for I := Low(Strings) to High(Strings) do
  Result := Result or (Value = Strings[I]);
end;

In fact, you do compare MyString with each string in Strings. As soon as you find one matching you can exit the for loop.

edited Oct 29 '08 at 13:02

answered Oct 29 '08 at 12:49

Burkhard

14,596
22
87
108

This works, please update your code with the Delphi one: function StringInArray(Value: string; Strings: array of string): Boolean; var I: Integer; begin Result := False; for I := Low(Strings) to High(Strings) do Result := Result or (Value = Strings[I]); end; – Fabio Gomes Oct 29 '08 at 12:57

Best way to find if a string is in a list (without generics)

3 Answers3

Linked