Write to files in Delphi

Question

I'm doing a program in Delphi, writing in all kinds of files, either text or executable:

var
 openfile: TextFile;
begin
 AssignFile(openfile, 'test.exe');
 Append(openfile);
 WriteLn(openfile,'[test]hi world[test]');
 CloseFile(openfile);
end;

How can I improve this?

• GiantTree: There are other ways using native file handles, but the way you have done it is the recommended one.
• Mawg: Although it might not be recommenced to write text to a file with a .EXE extension ,-)

Answer 1

Yes. I would add try..finally so that the file will be properly closed even in the case of exception (hopefully my remembrance of the syntax isn't too rusty):

var
 openfile: TextFile;
begin
 AssignFile(openfile, 'test.exe');
 Append(openfile);
 try
 WriteLn(openfile,'[test]hi world[test]');
 finally
 CloseFile(openfile);
 end;
end;

also, you say you want to write binary files as well as text files.. so don't use TextFile. The "modern" way would be to use TFileStream:

with TFileStream.Create('test.exe', fmOpenWrite) do
try
 Seek(0,soFromEnd);
 Write(...);
finally
 Free;
end;

Answer 2

Please note that AssignFile routines are very old fashioned. Consider using OOP approach using streams, like

var
 f: TFileStream;
begin
 f:=TFileStream.Create(FileName, fmCreate);
 try
 f.WriteBuffer(Pointer(SourceString)^, Length(SourceString));
 finally
 f.Free;
 end;
end;

(SourceString in this case should be AnsiString. It needs a little change for Unicode)

• Andrea Raimondi: What's wrong with using TStringStream and copying from that?
• smooty86: TStringStream does not work directly with the file (not suitable if you work with large files) and you can't change just specific part of it - you have to load and save whole file.
• Andrea Raimondi: I am not sure we are on the same page here. What I am saying is: to copy a string, why can't you use a TStringStream and then CopyFrom there. TStringStream allows you to seek and read specific strings, so it does precisely what you say it doesn't do. Or I am missing something.
• smooty86: This topic is "Write to files". TStringStream is a memory stream, you have to load whole file into memory, change it and save it = overwrite whole file.