"Albrecht Fritzsche" wrote in message news:3D58B5C7.1080008@tiscali-dsl.de...

Edward Diener wrote:

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class Publisher { typedef boost::function<void> Function; public: void SetChecker(const Function& Callback){ } void Publish(){} };

class Manager { public: Manager(); private: void Check() {} };

Manager::Manager() { Publisher d; d.SetChecker(std::mem_fun(&Manager::Check));

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try: d.SetChecker(boost::bind(&Manager::Check,this));

Brilliant - thanks! Would you mind giving me a short rationale about this, since I am a newbie regarding function pointers and function (object?) adaptors.

SO, if using an stl algorithm like

vector<Publisher> p; for_each(p.begin(), p.end(), mem_fun(&Publisher::Publish));

I don't have to bind anything, do I? mem_fun() returns a mem_fun_t functor object, which will receive the Publisher object pointer through each intern for_each call?

The function adaptor which mem_fun becomes takes a pointer or reference to its type as its single argument in order to call the member function. The for_each algorithm passes such a reference to each type in its internal loop, so everything is in sync.

And that object pointer passing was missing in my code and was achieved in your code through the binding?

In the boost::bind case, for a member function, you need to bind in a pointer to the actual object, which passing the "this" parameter does effectively. You don't need mem_fun with boost::bind, ie. d.SetChecker(boost::bind(std::mem_fun(&Manager::Check),this)); since boost::bind is smart and automatically knows how to bind member functions.

I had already looked at boost::bind but still cannot figure out its interface

template unspecified-3-1 bind(F f, A1 a1);

I have already mentioned to Peter Dimov that the doc for boost::bind might be updated to be more easily understandable. The boost::bind syntax creates a function adaptor, which is what boost::function wants. It is a much smarter version of the C++ standard library's std::bind1st and std::bind2nd with, more or less, unlimited parameters and types. I suggest you first look at the standard library versions and then re-read boost::bind documentation.

From: "Albrecht Fritzsche"

And that object pointer passing was missing in my code and was achieved in your code through the binding? I had already looked at boost::bind but still cannot figure out its interface

template unspecified-3-1 bind(F f, A1 a1);

What is this returning?

Following the boost::bind reference is not an easy task. :-) First, you need template unspecified-5 bind(R (T::*f) (), A1 a1) Effects: equivalent to bind<R>(boost::mem_fn(f), a1); since the first argument is a member function. This redirects you to template unspecified-3 bind(F f, A1 a1) Returns: a function object λ such that the expression λ(v1, v2, ..., vm) is equivalent to f(µ(a1, v1, v2, ..., vm)), implicitly converted to R. Throws: Nothing unless the copy constructors of F or A1 throw an exception. and all this translated to English means that boost::bind(&Manager::Check, this) returns a function object that, when called, returns boost::mem_fn(&Manager::Check)(this) that, in turn (see the mem_fn documentation) is equivalent to (this->*&Manager::Check)(); The thing to remember is that member functions have an additional implicit argument, the object pointer/reference.