{SOVED} how to check to see if TStringList has been created?

[Michl]

Offtopic: @mangakissa, you can left away your outer exception block, it has no function.

If you want you can play with this (no Debugger but enabled Heaptrc):

Code: [Select]

function Test: TStringList;
begin
  Result:=TStringList.Create;
//  raise Exception.Create('TestException');
end;

procedure TForm1.Button1Click(Sender: TObject);
var FileList : TStringList;
begin
//  try
    try
      FileList := Test;
      ShowMessage(FileList.Text);
    except
      on E: Exception do
        ShowMessage('Exception: '+E.Message);
    end;
//  finally
    FileList.Free;
    ShowMessage('FileList.Free');
//  end;
end;    The result is the same, with and without the outer exception block.

[chain_reaction]

I don't like the current function :

Code: [Select]

Fileutil.FindAllFiles().
Most programmers included me, often forgot to deal with the instance created. Should it be changed to procedure?.

[mangakissa]

I haven't seen the function itself, but it's nothing more then using findfirst, findnext,findclose.

[mangakissa]

If you want you can play with this (no Debugger but enabled Heaptrc):

It could be, but how many people uses Heaptrc?
Does Lazarus/Delphi not using smart compiling?
I know Lazarus tells the developer id some code is useful or not.

[Leledumbo]

I don't like the current function :
...
Most programmers included me, often forgot to deal with the instance created. Should it be changed to procedure?.

This function has existed for quite a long time, and many programs have used it. I don't think it should be changed just because you often forget to free the created instance. You have heaptrace to help you catch dangling pointers, combined with lineinfo in can show exact location of the unfreed memory. Changing a routine signature is not something that could be done "just like that", especially in a big projects like this. FYI, sockets interfaces gets deprecated for 2-3 stable versions before obsoleted.

[jcmontherock]

Hy,
It seems that nobody answer to the first question: how do we know wether a StringList has been created or not. When we define a TStringList we can see that the variable is not Nil (as I see with the debuging). Has anybody a solution to this question ?

[MarkMLl]

I fail to see your problem. If the variable doesn't contain nil (i.e. qqq<>nil or Assigned(qqq)) then an object was created and must be freed.

MarkMLl

[lucamar]

And if you want to be absolutely sure that Assigned(MyStringList) returns the "correct" result you can always assign it Nil somewhere, like in the constructor of the container object. For example (adapt to your needs):

Code: Pascal  [Select][+][-]

1. type
2.   TSomeObject = class
3.     FSomeStrings: TStringList;
4.     constructor Create;
5.     destructor Destroy; override;
6.     procedure GetMeSomeStrings;
7.   end;
8.  
9. [...]
10.  
11. constructor TSomeObject.Create;
12. begin
13.   inherited Create;
14.   FSomeStrings := Nil;
15. end;
16.  
17. destructor TSomeObject.Destroy;
18. begin
19.   if Assigned(FSomeStrings) then
20.     FSomeStrings.Free;
21.   inherited Destroy;
22. end;
23.  
24. procedure TSomeObject.GetMeSomeStrings;
25. begin
26.   if Assigned(FSomeStrings) then
27.     FSomeStrings.Free;
28.   FSomeStrings := FindAllFiles(...);
29. end;

[jcmontherock]

You are right !... That solves my problem. Thanks to everybody.