我正在运行时创建一个T
XMLDocument实例,以加载和解析XML文件.您可以查看以下代码：
unit Unit1;
interface
uses
Windows,Messages,SysUtils,Variants,Classes,Graphics,Controls,Forms,Dialogs,xmldom,XMLIntf,msxmldom,XMLDoc,StdCtrls;
type
Txml = class(TForm)
// XMLDocument1: TXMLDocument;
Memo1: TMemo;
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
xml: Txml;
implementation
{$R *.dfm}
procedure Txml.FormCreate(Sender: TObject);
var i,j:integer;
aNode:IXMLNode;
ws:String;
XMLDocument1:TXMLDocument;
begin
Memo1.Lines.Clear;
XMLDocument1 := TXMLDocument.Create(nil);
try
XMLDocument1.LoadFromFile('C:\a.xml');
XMLDocument1.Active := true;
aNode := XMLDocument1.ChildNodes.First;
while aNode<>nil do
begin
for i := 0 to aNode.ChildNodes.Count-1 do
begin
if aNode.ChildNodes[i].NodeName = 'Role' then
begin
Memo1.Lines.Add('Tag - '+aNode.ChildNodes[i].ChildNodes['Tag'].Text);
for j := 0 to aNode.ChildNodes[i].ChildNodes.Count-1 do
if aNode.ChildNodes[i].ChildNodes[j].HasChildNodes then
begin
ws := VarToStr(aNode.ChildNodes[i].ChildNodes[j].ChildValues['Tag']);
if trim(ws)<>'' then
Memo1.Lines.Add(ws);
ws := VarToStr(aNode.ChildNodes[i].ChildNodes[j].ChildValues['Value']);
if trim(ws)<>'' then
Memo1.Lines.Add(ws);
end;
end;
end;
aNode := aNode.NextSibling;
end;
XMLDocument1.Active := false;
finally
FreeAndNil(XMLDocument1);
end;
end;
end.
问题是这会产生AV.正如您可能已经看到的那样,组件在表单之前(// XMLDocument1：TXMLDocument;).
为什么当组件在代码工作的表单上时,但是当我在运行时创建它时它会生成AV？
XMLDocument1 : IXMLDocument; //not TXMLDocument XMLDocument1 := LoadXMLDocument(...); FreeAndNil;// must be deleted
解决方法
据我所知,你应该使用接口IDoc：IXMLDocument;代替.
来自docs：
When TXMLDocument is created without an Owner,it behaves like an
interfaced object. That is,when all references to its interface are
released,the TXMLDocument instance is automatically freed. When
TXMLDocument is created with an Owner,however,it behaves like any
other component,and is freed by its Owner.
换句话说,在使用nil Owner创建TXMLDocument实例时,不要在实例上调用Free()或FreeAndNil(),并且必须将对象分配给IXMLDocument变量,以便正确管理其现在活动的引用计数.