删除 TList 中的 TList
我试图在 onDestroy 事件中释放 Tlist 中的 Tlist，而 FastMM4 引发访问冲突错误。这是代码片段。
procedure TSignalFrm.FormDestroy(Sender: TObject);
var
x,y: integer;
begin
for x := 0 to signalList.Count - 1 do
begin
for y:=0 to TSignal(SignalList.Items[x]).alarmList.Count-1 do
begin
TAlarm(TSignal(SignalList.Items[x]).alarmList.Items[y]).Free;
end;
TSignal(SignalList.Items[x]).AlarmList.Free;
TSignal(SignalList.Items[x]).Free;
end;
SignalList.Free;
end;
我在 TSignal(SignalList.items[x]).Free; 处收到访问冲突错误线。在释放 SignalList 项之前释放 AlarmList 项会引发访问冲突错误，但为什么呢？
更新：我在 Windows XP 上使用 Delphi 7.0。实际的 FastMM4 消息如下。
FastMM 检测到对已释放对象调用虚拟方法的尝试。现在将引发访问冲突以中止当前操作。
释放的对象类：TList
虚拟方法：Destroy
虚拟方法地址：427CF0
分配号为：80055
后面是大量的内存转储。
根据此 FastMM4 错误，如果释放另一个对象中的对象，也会自动释放所有者。我知道这不可能是真的，但如果我错了，请纠正我。
I am trying to free Tlist within a Tlist in a onDestroy event and FastMM4 is raising an access violation error. Here is the code snippet.
procedure TSignalFrm.FormDestroy(Sender: TObject);
var
x,y: integer;
begin
for x := 0 to signalList.Count - 1 do
begin
for y:=0 to TSignal(SignalList.Items[x]).alarmList.Count-1 do
begin
TAlarm(TSignal(SignalList.Items[x]).alarmList.Items[y]).Free;
end;
TSignal(SignalList.Items[x]).AlarmList.Free;
TSignal(SignalList.Items[x]).Free;
end;
SignalList.Free;
end;
I get access violation error at TSignal(SignalList.items[x]).Free; line. Freeing AlarmList items before freeing SignalList items raises the access violation error, but WHY?
Update: I am using Delphi 7.0 on Windows XP. The actual FastMM4 messages is as follows.
FastMM has detected an attempt to call a virtual method on a freed object. An access viloation will now be raised in order to abort the current operation.
Freed Object class: TList
Virtual method: Destroy
Virtual method address:427CF0
The allocation number was: 80055
Followed by a lots of memory dump.
According to this FastMM4 error, if you free an object within an another object, you automatically free the owner as well. I know that can't be true, but correct me if I am wrong.
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评论（2）
TSignal是否未在其析构函数中释放其AlarmList成员？ （我就是这样做的）。更新：如果删除
TSignal(SignalList.Items[x]).AlarmList.Free;行，它会起作用吗？第二次更新：
如果每个
TList的项目包含指向对象的指针，则需要释放它。您的问题是
TSignal不是TList。由于它负责释放其成员（例如 Alarmlist），因此不应显式释放该 Alarmlist。Does
TSignalnot free itsAlarmListmember in its destructor? (That’s how I would do this).Update: does it work if you remove the
TSignal(SignalList.Items[x]).AlarmList.Free;line?Second update:
Each
TList's items need to be freed, if it contains pointers to objects.Your problem was that
TSignalis not aTList. Since it takes care of freeing its members (such as the Alarmlist), that Alarmlist should not be freed explicitly.由于 TAlam 和 TSignal 都是对象（而不是记录），我相信您应该使用 TObjectList 而不是 TList。 TObjectList 有一个称为 OwnsObjects 的特殊属性，允许它在释放其内容时正确释放它。看看http://docwiki.embarcadero.com/VCL/XE/ en/Contnrs.TObjectList.OwnsObjects
建议不要使用 TList，除非您需要存储指针而不是对象。
Since TAlam and TSignal are both objects (not records) I believe you should use TObjectList instead of TList. TObjectList has a special property calld OwnsObjects that allows it to free it's contents properly as it is being freed. Check this out http://docwiki.embarcadero.com/VCL/XE/en/Contnrs.TObjectList.OwnsObjects
As an advice do not use TList unless you need to store pointers not objects.