[英]Delphi, how to free record in TList
我想知道释放记录的TList的最佳方法。
我有以下记录:
type
TPkBill = record
PkBill: integer;
Constructor Create(c_PkBill: integer);
constructor TPkBill.Create(c_PkBill: integer);
begin
PkBill := c_PkBill;
end;
我创建列表并用记录填充它:
procedure TfrmProject.lvBillDblClick(Sender: TObject);
var
i, iCount: integer;
item: TListItem;
oPkBill: TPkBill;
lstPkBill: Tlist;
begin
iCount := 0;
lstPkBill:= TList.Create;
//if an item is selected in lv
if (lvBill.ItemIndex = -1) then begin exit; end
else
begin
//Loop through all items and get selected item
for i := 0 to lvBill.Items.Count - 1 do
begin
item := lvBill.Items.Item[i];
if(item.Selected = true)then
begin
//create new item
oPkBill := TPkBill.Create(StrToInt(lvBill.Items[i].Caption));
//add it to a list
lstPkBill.Add(TObject(oPkBill));
//add up
iCount := iCount +1;
end;
end;
//Now we have a list ok pkBill
if(iCount > 1)then //other stuff I do
end
我希望能够释放TList并释放记录。
这是我已经尝试过的:
for i := 0 to lstPkBill.Count - 1 do
begin
//TObject(TPkBill(lstPkBill[i])).Free; //Acces violation at adress..
//FreeMem(TPkBill(lstPkBill[i])); //Incompatible types
//FreeMem(TObject(lstPkBill[i])); //Incompatible types
end;
lstPkBill.Clear;
FreeAndNil(lstPkBill);
感谢您的帮助,不胜感激!
您已经使用构造函数定义了一条记录。 调用记录构造函数不会像类构造函数那样在堆上分配内存。 您的oPkBill
变量存在于堆栈中。 调用oPkBill := TPkBill.Create(...)
仅填充该变量的成员。 然后,您将整个变量(仅包含一个Integer成员)类型转换为TObject
指针。 您实际上并没有为列表项在堆上分配任何内存,因此无需释放它们。
我怀疑您实际上想做的是更多这样的事情:
type
PPkBill = ^TPkBill;
TPkBill = record
PkBill: integer;
Constructor Create(c_PkBill: integer);
end;
constructor TPkBill.Create(c_PkBill: integer);
begin
PkBill := c_PkBill;
end;
procedure TfrmProject.lvBillDblClick(Sender: TObject);
var
i: Integer;
item: TListItem;
oPkBill: PPkBill;
lstPkBill: TList;
begin
if lvBill.ItemIndex = -1 then Exit;
//an item is selected in lv
lstPkBill := TList.Create;
try
//Loop through all items and get selected items
for i := 0 to lvBill.Items.Count - 1 do
begin
item := lvBill.Items.Item[i];
if item.Selected then
begin
//create new item
New(oPkBill);
try
oPkBill^ := TPkBill.Create(StrToInt(lvBill.Items[i].Caption));
//add it to a list
lstPkBill.Add(oPkBill);
except
Dispose(oPkBill);
raise;
end;
end;
end;
//Now we have a list ok pkBill
if (lstPkBill.Count > 1) then
begin
//other stuff I do
end;
finally
for i := 0 to lstPkBill.Count - 1 do
Dispose(PPkBill(lstPkBill[i]));
lstPkBill.Free;
end;
end;
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