How to save classic Delphi string to disk (and read them back)?

Question

I want to achieve a very very basic task in Delphi: to save a string to disk and load it back. It seems trivial but I had problems doing this TWICE since I upgraded to IOUti

Answer 1

Code based on David's suggestions:

{--------------------------------------------------------------------------------------------------
 READ/WRITE UNICODE
--------------------------------------------------------------------------------------------------}

procedure WriteToFile(CONST FileName: string; CONST aString: String; CONST WriteOp: WriteOperation= woOverwrite; WritePreamble: Boolean= FALSE); { Write Unicode strings to a UTF8 file. It can also write a preamble }
VAR
   Stream: TFileStream;
   Preamble: TBytes;
   sUTF8: RawByteString;
   aMode: Integer;
begin
 ForceDirectories(ExtractFilePath(FileName));

 if (WriteOp= woAppend) AND FileExists(FileName)
 then aMode := fmOpenReadWrite
 else aMode := fmCreate;

 Stream := TFileStream.Create(filename, aMode, fmShareDenyWrite);   { Allow read during our writes }
 TRY
  sUTF8 := Utf8Encode(aString);                                     { UTF16 to UTF8 encoding conversion. It will convert UnicodeString to WideString }

  if (aMode = fmCreate) AND WritePreamble then
   begin
    preamble := TEncoding.UTF8.GetPreamble;
    Stream.WriteBuffer( PAnsiChar(preamble)^, Length(preamble));
   end;

  if aMode = fmOpenReadWrite
  then Stream.Position:= Stream.Size;                               { Go to the end }

  Stream.WriteBuffer( PAnsiChar(sUTF8)^, Length(sUTF8) );
 FINALLY
   FreeAndNil(Stream);
 END;
end;


procedure WriteToFile (CONST FileName: string; CONST aString: AnsiString; CONST WriteOp: WriteOperation);
begin
 WriteToFile(FileName, String(aString), WriteOp, FALSE);
end;


function ReadFile(CONST FileName: string): String;  {Tries to autodetermine the file type (ANSI, UTF8, UTF16, etc). Works with UNC paths }
begin
 Result:= System.IOUtils.TFile.ReadAllText(FileName);
end;