Question

i need to inherit an interface with abstract methods , in VB/c# we simply override methods from our interface while there is no need to code for IUnknown or IDispatch methods

but in c++, after inheriting interface in class & overriding methods in interface, when i tried to instantiate derived class i am getting following error

error C2259:  Imyinterface  : cannot instantiate abstract class
1>          due to following members:



 HRESULT IUnknown::QueryInterface(const IID &,void **)  : is abstract
 ULONG IUnknown::AddRef(void)  : is abstract
  ULONG IUnknown::Release(void)  : is abstract

因此,我需要推翻/取消 IUn known 和 IDispatch 方法, 如 adref, Release, Query Interface, invoke, gettyinfo 。

as they appears to be standard functions ,where can i get their code/definitions e.g.ATL or or any typelib? or any references where i can get code/examples of above methods

Answer 1

_uery Interface :如果能够到达通过 GUID 所指定的界面,请在 eve /code> 参数中为界面设置一个指针;或者将 lese /code > 设置为 NULL 。返回相应的 HRESULT 。



AddRef :增加界面的引用数 。

 releasure :减少界面的引用数 。

我建议先买一本关于COM的好书,然后再仔细研究。 旧版的< a href="https://rads. stackoverflow.com/amzn/click/com/ 1572313498" rel=“ nofollow noreferrer”>Inside Com (微软编程系列), 由 Dale Rogerson < /a > 编写, 是便宜的。 它确实有实例。 阅读亚马逊的评论, 以确定您是否愿意买下这本书 。

Answer 2

You need to override those methods and provide their definitions(in your derived class) and for all the functions declared pure virtual in your base class.
Unless you do so your derived class also acts as an abstract class and you cannot create any objects of it.

对于第二个问题,没有,我对这些方法的标准执行应该做些什么没有任何真正的好主意。

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