[Interest] Who disconnects lambda expression slots?

[Thiago Macieira]

On sábado, 15 de dezembro de 2012 05.46.39, Nikos Chantziaras wrote:
> On 15/12/12 05:19, Thiago Macieira wrote:
> > On sábado, 15 de dezembro de 2012 03.45.56, Nikos Chantziaras wrote:
> >> So I take it that means we should always manually disconnect in such
> >> cases.  Thinking about it, it seems possible to have done this
> >> automatically, but only for QObjects and through a connect() function
> >> 
> >> that would accept:
> >>       connect(const QObject* sender, PointerToMemberFunction signal,
> >>       
> >>               const QObject* receiver, Functor functor);
> >> 
> >> In that case, connect() would be able to know when 'receiver' gets
> >> destroyed and automatically do a disconnect.
> > 
> > It automatically disconnects when the destruction reaches the QObject
> > destructor.
> 
> Which QObject destructor?  The receiver is being destroyed before the
> sender:

The receiver's. If the signal is emitted *during* the receiver's destruction, 
you have to analyse this case.

>    class Foo: public QObject {
>        Q_OBJECT
>    public:
>        Foo(QObject* obj)
>        {
>            QObject::connect(obj, &QObject::objectNameChanged,
>            [this](const QString& objectName) {
>                ++this->i;
>            });
>        {
> 
>        int i = 0;
> 
>        //...
>    };
> 
>    // ...
>    Foo* foo = new Foo(someQObjectPtr);
>    delete foo;
> 
> So how does the destructor of Foo know how to disconnect when foo is
> deleted?

I don't see your point. QObject::connect adds the connection object to a list. 
QObject::~QObject destroys the list.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center
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