<![CDATA[size : 2254
uploaded_on : Tue Apr 6 00:00:00 1999
modified_on : Wed Dec 8 14:03:38 1999
title : TList example
org_filename : TListEx.txt
author : Theo Bebekis
authoremail : bebekis@otenet.gr
description : An example of using TList
keywords :
tested : not tested yet
submitted_by : The CKB Crew
submitted_by_email : ckb@netalive.org
uploaded_by : nobody
modified_by : nobody
owner : nobody
lang : plain
file-type : text/plain
category : delphi-misc
__END_OF_HEADER__
procedure TForm1.Button1Click(Sender: TObject);
var
MyComponent : TComponent;
i : PInteger;
List : TList;
begin
List := TList.Create;
{ get memory for an integer }
GetMem( i, SizeOf(integer));
{ assign it a value and add it to the list.
because it is the first addition it goes to
position zero }
i^:= 5;
List.Add(i);
{ typecast list's zero item to integer
convert it to string
and show it}
ShowMessage( IntToStr(Integer(List[0]^)) );
{ free the mem and nilify the zero item }
FreeMem( i, SizeOf(integer));
List[0] := nil;
{ now create a component }
MyComponent := TComponent.Create(nil);
{ and INSERT it to zero position
zero position still exists while
we do not delete it}
List.Insert(0, MyComponent);
{ typecast the zero item... etc... }
TComponent(List[0]).Name := 'MyNiceComponent';
ShowMessage(MyComponent.Name);
// it could be : ShowMessage(TComponent(List[0]).Name );
TComponent(List[0]).Free;
List.Free;
end;
We need to be very carefull when working with those lists.
It is very easy to have memory leaks or access violations
if forget what you are doing.
If you alreade have added an item to that index then it is possible to update an
object at the refered index.
But do not forget to deallocate the memory.
Here is the variation
procedure TForm1.Button1Click(Sender: TObject);
var
MyComponent : TComponent;
i : PInteger;
List : TList;
begin
List := TList.Create;
{ get memory for an integer }
GetMem( i, SizeOf(integer));
{ assign it a value and add it to the list.
because it is the first addition it goes to
position zero }
i^:= 5;
List.Add(i);
{ typecast list's zero item to integer
convert it to string
and show it}
ShowMessage( IntToStr(Integer(List[0]^)) );
{ nilify the zero item }
List[0] := nil;
{ now create a component }
MyComponent := TComponent.Create(nil);
{ and store it to zero position }
List[0] := MyComponent;
{ typecast the zero item... etc... }
TComponent(List[0]).Name := 'MyNiceComponent';
ShowMessage(TComponent(List[0]).Name);
MyComponent.Free;
FreeMem( i, SizeOf(integer)); { do not forget this }
List.Free;
end;
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