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A few succinct points about Event Handling in COM :
In COM, event handling is achieved via Connection Points. The COM object which fires events is a Connection Point Container. It recognizes several Connection Points which are actually interface methods that must be implemented by a Client Event Listener.
Hence,
COM Object That Fires Events
- implements IConnectionPointContainer.
- contains one or more IConnectionPoint implementations.
- calls event interface methods implemented by clients event listeners.
COM Client that listens to events
- implements Event Interface methods which are fired by COM Object.
- searches for a suitable connection point in event firing COM object via IConnectionPointContainer.FindConnectionPoint().
- connects with event firing object via IConnectionPoint.Advise().
- disconnects with event firing obejct via IConnectionPoint.Unadvise().
Regards,
Bio.
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Hi Bio,
I need to write a straight C++ client, not COM. I saw books talking about using sink object for the client, but not very sure how to write it, Do you know how to do that?
Thanks.
littlecuttiepie
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Hello littlecuttiepie,
>> I need to write a straight C++ client, not COM.
I understand your situation. I believe that what you are trying to say is that your client application is not an ATL-generated. The example code that I'll be sending to you is not ATL-generated. However, you -will- need to add some basic COM code into your client app (e.g. CoInitialize() and CoUnititalize(), and, depending on whether you used #import, you may need to either use smart pointers or use CoCreateInstance()).
>> I saw books talking about using sink object for the client, but not very sure how to write it, Do you know how to do that?
Yes, the sample code that I'm sending you contains an actual implementation of a sink object.
I'm currently writing a CodeProject article based on the sample code. Watch out for it as it will contain the documentation for my code.
Best Regards,
Bio.
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Hello littlecuttiepie,
I have uploaded my code project article :
TEventHandler - A C++ COM Event Handler For IDispatch-Based Events
It is in the latest updates section.
Regards,
Bio.
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All,
I was wondering if anyone could recommend JazzAge[^] or another similar product to accomplish this task. If you would recommend Jazzage, which version have you used?
Thanks,
Rich
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i'm a beginner in com development. can somebody help me to write a com addin for ms project..... thank you........
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Hi ,
Does anyone know if the functions in COM interface can be overloaded or not?
Thank you.
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tpndtbk wrote:
Does anyone know if the functions in COM interface can be overloaded or not?
Nope It Not Possible,Actually Component Technology to Interlink Langauges and concept like Function overloading,Inheritance etc. cannot be found in every language.
so that why Com developer has sacrfice many thing Good Programming Concepts to Create Component.
-----------------------------
"I Think this Will Help"
-----------------------------
Alok Gupta
visit me at http://www.thisisalok.tk
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If you are looking at it from the client side then instead of trying to overload the com interface simply create an interface wrapper for the COM object in your client. Your code would then sit inbetween your main client and the COM interface. For info on interface wrappers look here[^]
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You could also take a look at aggregation and containment if you are trying to perform it from the server side. It is not necessarily that COM doesn't support good programming practice, the whole reason for the development of COM was to insulate the client from the details of implementation; thus implementation inheritance is out of the question since it requires too much detailed information over how the "insides" work. COM does support interface inheritance, which is developed through aggregation and containment. These tools allow you to specialize COM interfaces.
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I wrote a piece of code as
hr = CoCreateInstance (&CLSID_DataAccessClient, NULL, CLSCTX_INPROC_SERVER, &IID_IDataAccessClient, &pCOM);
where pCom is of type IDataAccessClient.
The program throws a Fatal error as:
Fatal execution engine error.
Please help me out by giving some suggestions.
Biswa
Email: biswaranjan.rath@amdocs.com
Phone No: 09373311346
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Try this instead:
hr = ::CoCreateInstance(CLSID_DataAccessClient,
NULL,
CLSCTX_INPROC_SERVER,
IID_IDataAccessClient,
(void**)&pCOM);
if(FAILED(hr))
{...}
Notice the absence of the & operator.
I Dream of Absolute Zero
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I tried those options, but i'm using a reference so '&' is needed. again i tried this with (void**). still i got the error. Even this call doesn't return a status.
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Ok. I'm still not quite sure why you need to pass the address of the GUIDs like you did though.
The only other possibility that I can think of is that the COM library was not initialised. Have you called ::CoInitialize(NULL) at the start of your program?
I Dream of Absolute Zero
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I have initialized thye COM library by:
hr = CoInitialize(NULL);
after that i checked the status of hr, which is returning success.
then the program fails in CoCreateInstance()
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biswaranjan_rath wrote:
hr = CoCreateInstance (&CLSID_DataAccessClient, NULL, CLSCTX_INPROC_SERVER, &IID_IDataAccessClient, &pCOM);
What is Return Value of hr here
-----------------------------
"I Think this Will Help"
-----------------------------
Alok Gupta
visit me at http://www.thisisalok.tk
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Hello everyone. I know this is a newbie question but I have to ask. I am pretty comfortable with windows programming in C and C++ as a whole however I am still sketchy over COM development. Specifically I would like to tie in my office solutions to my Visual studio solutions. I understand that interacting with Office requires COm deployment and I was hoping someone might point me in the right direction for finding a good reference. When I first started Windows programming I was told to get Petzold's book. I think it was one of the best investments I ever made. I was wondering and hoping frankly, that there was an equivalent to that with respect to COM programming.
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Hi,
You can check my COM BLOG[^]. I have listed some good book names and useful URL's (Notes: These are my personal favourites)
Have a great day ahead!
Regards,
Sohail Kadiwala
(My Blog - http://blogs.wdevs.com/sohail/[^])
modified 21-Apr-21 21:01pm.
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I have just ordered a copy of Inside COM and I was looking into Inside OLE. I was wondering if anyone has read these books or have any other suggestions.
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Hi Folks,
I am writing an Attributed COM component in Visual C++ 7.1. In standard cases, the name of the coclass is the same as the CLASS name. I want to know if it is possible to change the coclass name ?
For instance, in the following code of mine, IDL will be generated with the coclass named as "CMyData". But, I want to have the coclass name as "MyData" without changing the actual class name.
[CODE]
[
object,
uuid("19088A64-4E82-4FD7-A8A5-A9FEE2577FE8"),
dual, helpstring("IMyData Interface"),
pointer_default(unique)
]
__interface IMyData : IDispatch
{
[id(1), helpstring("method MyMethod")] HRESULT MyMethod();
}
[
coclass,
threading("apartment"),
support_error_info("IMyData"),
vi_progid("MyComponent.MyData"),
progid("MyComponent.MyData.1"),
version(1.0),
uuid("4AF80BC4-6A51-4E83-A3A0-9184230CD2AD"),
helpstring("MyData Class")
]
class ATL_NO_VTABLE CMyData : public IMyData
{
public:
CMyData();
virtual CMyData();
DECLARE_PROTECT_FINAL_CONSTRUCT()
HRESULT FinalConstruct()
{
return S_OK;
}
void FinalRelease()
{
}
STDMETHOD(MyMethod)(void);
}
[/CODE]
Any help would be appreciated.
Regards,
Arun.
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I am trying to develop a COM addin for Outlook 2003 using C#. I have read Hannes Pavelka's article on creating toolbars and buttons in Outlook. But, every button that I added only shows up in the main Outlook window. I'm not able to get anything new to show up in the message composition window. Does anyone know how to do this?
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The GnucDNA is a component for building P2P applications. It is written in C++. Examples of how to call it from VB.NET and C#.NET can be seen at http://www.gnucleus.com/GnucDNA/docs/examples.html. Works fine for most methods in GnucDNA, but one crucial call to a method called SetSharedDirs is not shown in the examples, and for a good reason: It does not work, it requires the argument to be passed as a string array pointer.
Looks like Microsoft is trying to explain something about how to do it by marshalling at http://samples.gotdotnet.com/quickstart/howto/doc/Interop/StringMarshal.aspx. Also, seem like using unmanaged code in C# by declaring keyword “unsafe” and statement “fixed” may hold a key, but how?
The C++ - method in the .COM can be seen at http://cvs.sourceforge.net/viewcvs.py/gnucleus/GnucDNAR2/ComShare.cpp?sortby=date&view=markup, and looks like so:
void CComShare::SetSharedDirs(VARIANT* pDirPaths)
Anybody able to come up with a call from VB.NET or C#.NET that does not produce a type mismatch – error?
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I hope someone might be able to answer this puzzle that I've found while testing a component of mine.
I am using Excel's VBA environment to quickly test a few of the methods in my component. Now if I create my component, specifying the type explicitly and run the method, everything works OK.
eg:
<code>
Dim Obj as MyItem
Dim strTitle As String
Set Obj = New MyItem
strTitle = "Some Description"
call Obj.SetTitle(2057, strTitle)
Set Obj = Nothing
</code>
Now here's the weird bit. If I create my item from an Object variable, it fails on my call to the same method. So if I change my code to:
<code>
dim Obj as Object
Dim strTitle As String
Set Obj = New MyItem
strTitle = "Some Description"
<font color=red>call Obj.SetTitle(2057, strTitle)</font><font color=green>' This FAILS with 'Type Mismatch' error </font>
Set Obj = Nothing
</code>
I can get access to the other properties of the item, but for some reason, it will not call this function.
Am I missing something?
There must be a simple explanation for this.
I Dream of Absolute Zero
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UPDATE
Its gets stranger.
If I replace the String variable by a litteral text, it works!!
call Obj.SetTitle(2057, "Hello") 'Works!!
WTF! Are string types treated differently when called via an Object type?
Why is this happening ? Someone enlighten me.
I Dream of Absolute Zero
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Are string types treated differently when called via an Object type?
Of course. Strings can be passed by VARIANT with VT_BSTR (your second case) or VT_BSTR|VT_BYREF (your first case).
Probably, the Invoke-helper for your class cannot process this vt-value.
Set the breakpoint inside Invoke(...) of your class and test it.
PS
Your can also get the valid result with extra parentheses around String.
call Obj.SetTitle(2057, (strTitle))
With best wishes,
Vita
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