[PyQt] Keeping the wrapper alive when it would go out of scope

[Phil Thompson]

On 4 Dec 2018, at 9:06 am, Phil Thompson <phil at riverbankcomputing.com> wrote:
> 
> On 4 Dec 2018, at 1:42 am, Nyall Dawson <nyall.dawson at gmail.com> wrote:
>> 
>> Hi list,
>> 
>> If I have a method in a class with a /Transfer/ed argument:
>> 
>>  void addTask( MyClass* task /Transfer/ );
>> 
>> and I attempt to call it from a code which looks like this:
>> 
>>  def scoped_function():
>>       t = MyClass()
>>       t.some_python_property = 555
>>       m.addTask( t )
>> 
>>  scoped_function()
>> 
>> Then the Python wrapper for t (but not the transferred cpp object) is
>> deleted when t goes out of scope at the end of the function call, as
>> expected.
>> 
>> Is there anyway to indicate to sip that the lifetime of the wrapper
>> should be bound to the cpp object, and only deleted when the cpp
>> object is? What I'm trying to achieve is that the wrapper, including
>> the python-only "some_python_property", is not cleaned up when
>> scoped_function() exits, and is instead only cleaned up when the
>> MyClass cpp base class object is deleted.
> 
> That is what /Transfer/ does. You need to provide a complete test to demonstrate the problem.

Also, you could call sip.dump(t) either side of the call to addTask() to see the effects.

Phil