我有一个带有iFrame的TEmbeddedWB(
https://sourceforge.net/projects/embeddedwb/).我必须找出特定的HTML标签是否在iFrame内部.我的iFrame对象是IHTMLFrameBase2,而Tag是IHTMLElement.我知道iFrame.contentWindow.document(它是一个IHTMLDocument2)与Tag.document相同.但Tag.document是一个IDispatch对象,因此下面给出了一个false：
if iFrame.contentWindow.document = Tag.document then ShowMessage('In iFrame')
else ShowMessage('Not in iFrame');
我知道这两个对象是一样的,因为Watch List可以显示它们的内存地址：
Addr(iFrame.contentWindow.document) // Gives variable required error @iFrame.contentWindow.document // Gives variable required error Pointer(iFrame.contentWindow.document) //Compiles,but gives wrong address Format('%p',[iFrame.contentWindow.document]) //Compiles,but gives EConvertError
解决方法
从
rules of COM：
It is required that any call to QueryInterface on any interface for a given object instance for the specific interface IUnknown must always return the same physical pointer value. This enables calling QueryInterface(IID_IUnknown,…) on any two interfaces and comparing the results to determine whether they point to the same instance of an object (the same COM object identity).
所以,问他们两个IUnknown接口,并进行比较.
var disp: IDispatch; doc: IHTMLDocument2; .... if (disp as IUnknown) = (doc as IUnknown) then ....