Re: [Boost-users] pattern support for traversing inheritance chain

On Wed, Nov 7, 2012 at 3:21 PM, Nathan Crookston

wrote:

Hi Brian,

On Wed, Nov 7, 2012 at 4:04 PM, Brian Budge wrote:

...

Hi all -

I have a case where I have a largeish inheritance hierarchy. I will be calling an initialization function on all objects before using them in some fashion.

Basically what I need to happen is when I call init() on a Foo the following would occur:

void Foo::init() { super::init(); // now with the knowledge that anything I inherited is set up, I can set myself up... }

When I'm dealing with a situation like you describe (not using constructors), I find that Boost.Signals (or Signals2) do what I'm looking for.

I generally do something like the following:

class B { typedef boost::signal OnInitListener; OnInitListener onInit_; public: boost::signals::connection connectOnInitListener(OnInitListener::slot_function_type cb) { return onInit_.connect(cb); }

void onInit() { onInit_(); } };

class D : public B { D() { connectOnInitListener(bind(&D::onInitImpl, this)); } // Register our onInit handler. };

//Repeat for further derivatives.

This means I don't need to state whom I inherit from, the order of calling is determined by the order of construction, and if one method doesn't need to listen for the onInit signal, everything works as expected.

HTH, Nate

Hi Nate - Yes, this seems quite useful. With signal connect, I guess it's more-or-less pushing-back on a list of function objects? When the signal is called, it iterates the list and calls each function object? Thanks for the suggestion. Seems like a good way to go. Brian