Moving a list into another

Good morning,
could anyone help me in this?

In Delphi-6 I have a piece of code which declares
var MyList, TempList: TList;

MyList has some items. TempList has the same items in a different order. Both lists refer to pointers of the same type.
How can I move TempList to the var MyList? I do not wish to execute re-ordering directly in MyList since it might no be definitive.

When I assign
MyList := TempList;
all looks fine, although freeing lists produces following error
"Access violation at address [addr]. Read of address [addr]"

Thank you for the attention
Nikiforos

Delphi

Last Comment

nikif

8/22/2022 - Mon

MerijnB

3/6/2015

The reason you get the access violation, is (at least I assume) that you free TempList.
When you do MyList := TempList, both vars point to the same list, if you that list, both variables become invalid.

try something like:

var MyList: TList;
    TempList: TList;
    i: integer;
begin
 MyList := TList.Create();
 TempList := TList.Create();
 
 try
  // add your stuff to the lists
  
  
  // now we do the actual moving from TempList to MyList
  for i := 0 to TempList.Count - 1 do
   if MyList.IndexOf(TempList[i]) = -1 then  // check if MyList does not (already) contain this pointer in TempList
    MyList.Add(TempList[i]);                 // if not add it to MyList
	
  // now all pointers which were not (yet) in MyList were added from TempList
  // if you want to remove them from TempList call TempList.Clear();
  
  // TempList.Clear();  // uncomment this line if you want to remove the pointers from TempList
 finally
  MyList.Free();
  TempList.Free();
 end;
end;

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nikif

3/6/2015

ASKER

Dear MerijnB thank you for your attention,

Unfortunately what you proposed does not work as I expected.
Let's say MyList contains items A-B-C-D-E-F-G
TempList contains items A-F-E-D-C-B-G

Your proposition copies all pointers to MyList, so in line 18 MyList comes with items A-B-C-D-E-F-G-A-F-E-D-C-B-G
My aim is MyList with items A-F-E-D-C-B-G

Thank you
Nikiforos

ASKER CERTIFIED SOLUTION

MerijnB

3/6/2015

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