如何将未知接口保存到指针？ [英] How to save an unknown Interface to a Pointer?

问题描述

例如，我有一个未知界面，并希望将其保存到TreeNode Data？

  var 
 X：Inknown; 
  

要保存：

  .... 
 Node：= TreeView1.Items.Add; 
 //Node.data:=x; //编译器不会允许这个
 Node.data:=@x; 
 ... 
  

获取：

  ... 
 var 
 //X:=Node.data; //编译器也不会允许这个
指针（X）：= Node.data; //一个异常捕获
 ... 
  

解决方案

一个接口是一个指针，所以你可以按原样存储它（不要使用 @ 运算符）。然而，为了确保接口的使用寿命，只要节点引用​​它，就必须手动递增/递减其引用计数，例如：

  Node：= TreeView1.Items.Add; 
 Node.Data：=指针（x）; 
 x._AddRef; 
  

  x：= IUnknown（Node.Data）; 
  

  procedure TMyForm.TreeView1Deletion（Sender：TObject; Node：TTreeNode）; 
 begin 
 IUnknown（Node.Data）._ Release; 
结束
  

Can I save an unknown interface to a pointer ?

For example I have an unknown interface and want to save it to a TreeNode Data?

var
  X : Inknown;

To save :

....  
  Node:=TreeView1.Items.Add;
  //Node.data:=x; //compiler won't allow this
  Node.data:=@x;
...  

To get :

...  
var
  //X:=Node.data; //compiler won't allow this too
  Pointer(X):=Node.data; //an exception caught
...  

解决方案

An interface is a pointer, so you can store it as-is (don't use the @ operator). However, to ensure the interface's lifetime, you have to increment/decrement its reference count manually for as long as the node refers to it, eg:

Node := TreeView1.Items.Add;
Node.Data := Pointer(x);
x._AddRef;

x := IUnknown(Node.Data);

procedure TMyForm.TreeView1Deletion(Sender: TObject; Node: TTreeNode);
begin
   IUnknown(Node.Data)._Release;
end;

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