Search a String array in Delphi - delphi

Question

Is there a function in the Delphi standard library to search string arrays for a particular value?
e.g.
someArray:=TArray<string>.Create('One','Two','Three');
if ArrayContains(someArray, 'Two') then
ShowMessage('It contains Two');

Answer 1

There is absolutely no need to reinvent the wheel. StrUtils.MatchStr does the job.
procedure TForm1.FormCreate(Sender: TObject);
var
someArray: TArray<string>;
begin
someArray:=TArray<string>.Create('One','Two','Three');
if MatchStr('Two', someArray) then
ShowMessage('It contains Two');
end;
Note the parameter order convention.
Another note: MatchStr is a canonicalized name assigned to this function somewhen in between Delphi 7 and Delphi 2007. Historical name is AnsiMatchStr (convention is the same as in the rest of RTL: Str/Text suffix for case-sensitivity, Ansi prefix for MBCS/Locale)

Answer 2

I wrote one I modeled after the old Clipper AScan function (tested in XE). #RRUZ's answer is more correct (there is one existing), but mine doesn't require the array to be sorted first and is fast enough on small arrays. (It also works in pre-generics versions of Delphi.) I also overload it for various types of array - here are the implementations for string and integer:
// Returns the 0-based index of Value if it's found in the array,
// -1 if not. (Similar to TStrings.IndexOf)
function AScan(const Ar: array of string; const Value: string): Integer; overload;
var
i: Integer;
begin
Result := -1;
for i := Low(Ar) to High(Ar) do
if SameText(Ar[i], Value) then
begin
Result := i;
Break
end;
end;
function AScan(const Ar: array of Integer; const Value: Integer): Integer; overload;
var
i: Integer;
begin
Result := -1;
for i := Low(Ar) to High(Ar) do
if (Ar[i] = Value) then
begin
Result := i;
Break
end;
end;
procedure TForm2.FormShow(Sender: TObject);
var
someStrArray: TArray<string>;
someIntArray: TArray<Integer>;
Idx: Integer;
begin
someStrArray := TArray<string>.Create('One', 'Two', 'Three');
Idx := AScan(someStrArray, 'Two');
if Idx > -1 then
ShowMessage(Format('It contains Two at index %d', [Idx]))
else
ShowMessage('Not found');
someIntArray := TArray<Integer>.Create(8, 16, 32);
Idx := AScan(someIntArray, 32);
if Idx > -1 then
ShowMessage(Format('It contains 32 at %d', [Idx]))
else
ShowMessage('16 not found');
end;
For versions of Delphi that support generics, here's a version that doesn't require the array to be sorted, and that also allows you to provide the comparison function if needed:
Interface:
type
TGenericsUtils = class
public
class function AScan<T>(const Arr: array of T; const Value: T; const Comparer: IEqualityComparer<T>): Integer; overload;
class function AScan<T>(const Arr: array of T; const Value: T): Integer; overload;
end;
Implementation
class function TGenericsUtils.AScan<T>(const Arr: array of T; const Value: T): Integer;
begin
Result := AScan<T>(Arr, Value, TEqualityComparer<T>.Default);
end;
class function TGenericsUtils.AScan<T>(const Arr: array of T; const Value: T;
const Comparer: IEqualityComparer<T>): Integer;
var
i: Integer;
begin
for i := Low(Arr) to High(Arr) do
if Comparer.Equals(Arr[i], Value) then
Exit(i);
Exit(-1);
end;
Test code:
var
AIntTest: TIntegerDynArray;
AStrTest: TStringDynArray;
begin
AIntTest := TIntegerDynArray.Create(12, 15, 6, 1, 4, 9, 5);
AStrTest := TStringDynArray.Create('One', 'Six', 'Three', 'Four', 'Twelve');
WriteLn('AIntTest contains 9 at index ', TGenericsUtils.AScan<Integer>(AIntTest, 9));
WriteLn('AStrTest contains ''Four'' at index ', TGenericsUtils.AScan<String>(AStrTest, 'Four'));
ReadLn;
end.

Answer 3

you can use the TArray.BinarySearch function, which is part of the Generics.Collections unit.
check this sample
{$APPTYPE CONSOLE}
{$R *.res}
uses
Generics.Defaults,
Generics.Collections,
System.SysUtils;
Var
someArray: TArray<string>;
FoundIndex : Integer;
begin
try
someArray:=TArray<string>.Create('a','b','c');
if TArray.BinarySearch<String>(someArray, 'b', FoundIndex, TStringComparer.Ordinal) then
Writeln(Format('Found in index %d',[FoundIndex]))
else
Writeln('Not Found');
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
Readln;
end.
Note: BinarySearch requires that the array be sorted.