explaination on assings and free parameters

Hello

What are the do and donn't when passing Lists from one procedure to another.

I do have three different procedures:

P;
var
LStringlist : TStringlist;
begin
LStringlist : TStringlist.create;

LStringlist.add

procedureTwo(Lstringlist);

if LStringlist <nil then
LStringlist.free;
end;

procedureTwo(AStringList : TStringlist = nil);
var
lStringlist : TStringlist;
begin
if AStringlist = nil then
lStringlist := TStringlist.create
else
lStringlist = AStringlist;

//do something

LStringlist.free;
end;

ProcedureThree
begin
proceduretwo;
end

I had an AV problem when freeeing the LStringlist in This was because it's already been freed in ProcedureTwo.
However where and when should the lStringlist in each procedure be freed?
( I thought that after lStringlist = AStringlist in procedureTwo and the LStringlist.free the original LStringlist in P would also have been freed; Debugging shows that this is not true. )

I hope your answers would help me understand how and when a parameter may and should be freed.

Regards

Andries




[Non-text portions of this message have been removed]

Hi,

procedureTwo(AStringList : TStringlist = nil);

Your code creates a new local StringList in procedureTwo.

Use a var parameter:

procedureTwo(var AStringList : TStringlist);

to pass the existing StringList, which is what I think you want.

Martin.