[Qt-interest] Signal chaining

[Mandeep Sandhu]

Thanks Rainer, this is what I've done currently! :)

Regards,
-mandeep

On Mon, Mar 29, 2010 at 6:45 PM, Rainer Wiesenfarth
<Rainer.Wiesenfarth at inpho.de> wrote:
>
> From: Mandeep Sandhu
>>
>> On Mon, Mar 29, 2010 at 5:43 PM, Andreas Pakulat <apaku at gmx.de> wrote:
>> >
>> > No you don't. You only need A and C visible in B, which can
>> then make the
>> > connection. Thats another nice thing about Qt's signal/slots you can
>>
>> Right. But I didn't want to make A visible in B, since all these
>> sub-level classes are helper classes and really shouldn't bother about
>> who's calling.
>
> I think it is possible with the visibility you would like if you do it like
> this (the //LOOK HERE comments indicate the important parts):
>
> ===== c.h =====
>
> class C : public QObject
> {
>    Q_OBJECT
>
> public:
>
>    ...
>
> signals:
>
>    void originalSignal ();
>
>    ...
> };
>
> ===== b.h =====
>
> class C;
>
> class B : public QObject
> {
>    Q_OBJECT
>
> public:
>
>    B ();
>    ...
>
> signals:
>
>    void forwardedSignal ();
>
>    ...
>
> private:
>
>    C   *m_pC;
> };
>
> ===== b.cpp =====
>
> #include <c.h>
>
> B::B ()
>    : m_pC (new C)
> {
>    //LOOK HERE:
>    // forward the signal of the (hidden) member to the
>    // application
>    connect (m_pC, SIGNAL(originalSignal())
>        , this, SIGNAL(forwardedSignal()));
>    ...
> }
>
> ===== a.h =====
>
> class B;
>
> class A : public Q_OBJECT
> {
>    Q_OBJECT
>
> public:
>
>    A ();
>    ...
>
> public slots:
>
>    void finalAction ();
>
>    ...
>
> private:
>
>    B   *m_pB;
> };
>
> ===== a.cpp ====
>
> #include <b.h>
>
> A::A ()
>    : m_pB (new B)
> {
>    //LOOK HERE:
>    // connect to the forwarded signal without knowledge
>    // on its originating class
>    connect (m_pB, SIGNAL(forwardedSignal())
>        , this, SLOT(finalAction()));
>    ...
> }
>
> void A::finalAction ()
> {
>    ...
> }
>
> Best Regards / Mit freundlichen Grüßen
> Rainer Wiesenfarth
>
> --
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