[DUG] Dumb Friday Question

[Leigh Wanstead]

SignatureI think PopulateList should be guarded by try.

Procedure DoSomthing;

Var

  List : TStrings;

Begin

List := TStringList.Create;

try

 PopulateList(List);

  if List.Count > 0 then

  begin

     .do lots of stuff with the list

  End;

Finally

  List.Free;

End;

End;



I would write this one like this

Procedure DoSomthing;

Var

  List : TStrings;

Begin

List := GetLoadsOfStrings;



  if assigned(List) then

  begin

try

     .do lots of stuff with the list

Finally

  List.Free;

End;

  End;

End;



Regards

Leigh

www.smootharm.com



  -----Original Message-----
  From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz]On
Behalf Of Tim Jarvis
  Sent: Friday, 4 May 2007 4:30 p.m.
  To: NZ Borland Developers Group - Delphi List; vss at vss.co.nz
  Subject: RE: [DUG] Dumb Friday Question


  Hi Guys,



  Hope you don't mind me sticking my nose in here. Firstly I agree with the
sentiment that you should try and avoid creating objects in one place and
freeing in another, however I don't think that this situation represents
that, think of a function that returns a class as a factory method, these
obviously are quite common and not bad practice at all, in fact a
constructor is a factory type method.



  Procedure DoSomthing;

  Var

    List : TStrings;

  Begin

  List := GetLoadsOfStrings;



  try

    if assigned(List) then

    begin

       .do lots of stuff with the list

    End;

  Finally

    List.Free;

  End;

  End;



  Is really not much different from



  Procedure DoSomthing;

  Var

    List : TStrings;

  Begin

  List := TStringList.Create;

   PopulateList(List);

  try

    if List.Count > 0 then

    begin

       .do lots of stuff with the list

    End;

  Finally

    List.Free;

  End;

  End;



  The issue is where the variable is declared, and the scope of the
ownership not the act of creation, creation is fine to delegate to a factory
type method.



  Regards Tim.




----------------------------------------------------------------------------
--

  From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz]
On Behalf Of Rohit Gupta
  Sent: Friday, 4 May 2007 12:22 PM
  To: vss at vss.co.nz; NZ Borland Developers Group - Delphi List
  Subject: Re: [DUG] Dumb Friday Question



  I would go along with Robert, you should not return complex types from
functions that create them,   It makes the code messy, you create it in one
place and free it in another.  Any sort of code analyser would also complain
about this.  You could return a string = stringlist.text and assign it to a
local stringlist.

  Jeremy Coulter wrote:

  Hi All. This is a question that might be infulenced by some serious lack
of sleep :-)



  I have a funtion. Its return result is a TStringlist.

  In my code I create a TStringlist then add my values to it, then pass this
to the RESULT varaible for the function.



  Now,  this is prob. an obvious answer than I prob. do actually know, but
if I got:-



  sResult := TStringList.create;

  sResult.add('blah');

  Result:=sResult;



  Then if I free sResult, then I loss the values I added, and the result is
empty as you would expect.

  But the issue I have is, so if I DONT free sResults, what happens to it?
Surley it stays in memory,a dn I would end up with a memory leack after
repeaditive calls. Is that right? Or is because the variable is function
specific its free by default etc?

  Its a basic question I know....but the more I thought about it the more
uncertain I became....I really need some sleep so that prob. the real
probelm :-)



  Jeremy







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  Rohit Gupta

  B.E. Elec.   M.E.   Mem IEEE    Associate IEE

  Technical Manager

  Computer Fanatics Limited



  Tel     +64 9 4892280

  Fax    +64 9 4892290

  Email  rohit at cfl.co.nz

  Web    www.cfl.co.nz




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