[PyQt] How to write handwritten code to access the C++ object when the corresponding python object destroyed?

[Phil Thompson]

Have a look at %MethodCode for dtors.

Phil

On 19/02/2020 14:19, Weitian Leung wrote:
> One more question, is it possible to insert handwritten code to the
> MappeedType's release_XXX?
> 
> When mapped one type to python's str, which type has it's own alloc 
> method
> (The BSTR for example, SysStringAlloc etc). After passed to the C++ 
> call
> and returned, we need to free the memory using it's own dealloc method.
> 
> So is it possible do that? Or other way to call the dealloc method...
> 
> On Wednesday, February 19, 2020, Weitian Leung <weitianleung at gmail.com>
> wrote:
>> Thanks, it works!
>> 
>> On Wednesday, February 19, 2020, Phil Thompson <
> phil at riverbankcomputing.com> wrote:
>>> On 17/02/2020 14:35, Weitian Leung wrote:
>>>> 
>>>> Hi,
>>>>     I'm noob in SIP. Say I have two abstract interfaces and one 
>>>> method
> to
>>>> create the object:
>>>> 
>>>> struct IUnknown /Abstract/
>>>>> 
>>>>> {
>>>>>     virtual void AddRef() = 0;
>>>>>     virtual void Release() = 0;
>>>>> 
>>>>>     %GCClearCode
>>>>>         printf("GCClearCode\n");
>>>>>     %End
>>>>> };
>>>>> 
>>>>> struct IDemo : public IUnknown /Abstract/
>>>>> {
>>>>>     virtual void SayHi() = 0;
>>>>> };
>>>>> 
>>>> 
>>>> void createDemo(IDemo **demo /Out/);
>>>>> 
>>>> 
>>>> 
>>>> Using in python side:
>>>> idemo = demo.createDemo()
>>>> idemo = None
>>>> 
>>>> Is it possible to write some handwritten code that call the Release
> method
>>>> when idemo set to None or when  idemo doing GC?
>>>> Or if we can call AddRef automatically when idemo assign to another
> object.
>>>> 
>>>> I known that on python side we can call AddRef/Release to make it 
>>>> works,
>>>> but I want the code more python's way.
>>>> 
>>>> The %GCClearCode handwritten code never called in this case.
>>>> And the %GCTraverseCode handwritten code only call when the object 
>>>> make
> an
>>>> assignment to other object.
>>>> Am I missing something?
>>>> 
>>>> Please check the full code in the  attached file.
>>> 
>>> 
> https://www.riverbankcomputing.com/static/Docs/sip/c_api.html#event-handlers
>>> 
>>> I've only just realised that that documentation is incomplete. The 
>>> two
> event types currently implemented are...
>>> 
>>> sipEventWrappedInstance,    /* After wrapping a C/C++ instance. */
>>> sipEventCollectingWrapper,  /* When garbage collecting a wrapper 
>>> object.
> */
>>> 
>>> ...and the corresponding event handler signatures are...
>>> 
>>> typedef void (*sipWrappedInstanceEventHandler)(void *sipCpp);
>>> typedef void (*sipCollectingWrapperEventHandler)(sipSimpleWrapper
> *sipSelf);
>>> 
>>> Phil
>>>