Chris Bensen has a 'small' tip, which in fact is a great tip.
He suggest to always pass strings as const or var. If you pass them by value extra (unnecessary) assembly is being generated.
Read his blogpost String parameters in delphi (Don't forget the comments)
Just installed the professional version of Eurekalog, which is, imo, a must have tool for tracking exceptions and memory leaks in your Delphi Win32 applications.
This tool, and of course any other tool out there that does the same, really helps you to track down exceptions fast. For me, even more important, is the fact that it helps you track down memory leaks as well.
No matter how secure you program, sooner or later, you will loose some memory. Here some pitfalls:
1. Let it be clear where, and who, will free the object
It must be clear where objects are created (read memory for the object is allocated) because otherwise you are in danger for memory leaks.
Functions that create their result are dangerous in this manner. Suppose a function that creates a TStringList, and returns it as it's result:
function TForm3.GetSomeStringList : TStrings;
begin
Result := TStringList.Create;
Result.Add('one');
Result.Add('two');
end;
procedure TForm3.DoSomethingWithaStringlist;
var
MyStringList : TStrings;
begin
MyStringList := GetSomeStringList;
try
ShowMessage(MyStringList.Text);
finally
MyStringList.Free; //Free it!
end;
end;
procedure TForm3.GetSomeStringList(
AStringList : TStrings);
begin
AStringList.Add('one');
AStringList.Add('two');
end;
procedure TForm3.DoSomethingWithaStringlist;
var
MyStringList : TStrings;
begin
MyStringList := TStringList.Create;
try
GetSomeStringList(MyStringList);
ShowMessage(MyStringList.Text);
finally
MyStringList.Free; //Free it!
end;
end;
It is better to have both, the Create and Free in the same try finally block if possible. Can't go wrong if you code it like this.
2. Always free your own objects nobody else does it for you
Sometimes it is easy to add to, for example a listbox, also an extra object with more information of the selected item. When filling the items (a TStringlist) you pass on a reference to the listbox item. Later you can use that information to do, whatever you want to do.
Your code could look like this:
procedure TForm3.Button1Click(Sender: TObject);
var
obj : TSomeObject;
begin
obj := TSomeObject.Create;
obj.SomeInfo := 'This is number one';
ListBox1.Items.AddObject('one', obj);
obj := TSomeObject.Create;
obj.SomeInfo := 'This is number two';
ListBox1.Items.AddObject('Two', obj);
end;
ShowMessage(
(ListBox1.Items.Objects[ListBox1.ItemIndex]
as TSomeObject).SomeInfo);
for i := 0 to ListBox1.Items.Count - 1 do begin
Listbox1.Items.Objects[i].Free;
end;
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