Class template active_function

poet::active_function — Create an active object from an ordinary function or object.

Synopsis

template<typename Signature> 
class active_function {
public:
  // types
  typedef boost::function_traits<Signature>::result_type passive_result_type;
  typedef poet::future<passive_result_type>              result_type;        
  typedef boost::slot<Signature> passive_slot_type;

  // construct/copy/destruct
  active_function(const passive_slot_type &, 
                  boost::shared_ptr<scheduler_base> = boost::shared_ptr<scheduler_base>());
  active_function(const active_function &);
  active_function();
  active_function& operator=(const active_function &);
  virtual ~active_function();

  // public member functions
  result_type operator()(future<T1>, future<T2>, ..., future<TN>);
  result_type operator()(future<T1>, future<T2>, ..., future<TN>) const;
  bool expired() const;
};

Description

An active_function can be created in one step from an ordinary function or function object. By default, an active_function is a fully functional active object with its own scheduler. Multiple active_functions may also share a scheduler and be combined to form more complicated active objects.

In the following, the active_function is taken to have a signature of: 

active_function<R (T1, T2, ..., TN)>

Example Code

active_function public types

  1. typedef boost::slot<Signature> passive_slot_type;

    Slot type for the passive function the active_function is constructed from.

active_function public construct/copy/destruct

  1. active_function(const passive_slot_type & passive_function, 
                boost::shared_ptr<scheduler_base> scheduler = boost::shared_ptr<scheduler_base>());

    Parameters:

    passive_function

    The underlying function this active_function object will call. The boost::slot class supports tracking of arbitrary boost::shared_ptr which are associated with the slot. For example, if the slot is constructed from a non-static member function, the lifetime of the member function's object can be tracked and the slot prevented from running after the object is destroyed.

    scheduler

    Specify a scheduler object for the active_function to post its method requests to. By default, a new Scheduler object is created for the active_function. If the active_function is providing a method as part of an active object class, you may wish for all the class' methods to share the same scheduler. 

  2. active_function(const active_function & other);

    The copy constructor creates a shallow copy of other. Both copies share the same scheduler and passive function. 

  3. active_function();

    The default constructor creates an empty active_function which cannot be used until it is assigned a useable active_function.

  4. active_function& operator=(const active_function & rhs);

    Assignment turns *this into a shallow copy of rhs. Both copies share the same scheduler and passive function. 

  5. virtual ~active_function();

    Virtual destructor.

active_function public member functions

  1. result_type operator()(future<T1> arg1, future<T2> arg2, ..., future<TN> argN);
result_type operator()(future<T1> arg1, future<T2> arg2, ..., future<TN> argN) const;

    Invocation creates a method request and sends it to the active_function's scheduler. The method request may be cancelled by calling future::cancel() on the returned future.

    Note the active_function takes futures as arguments, as well as returning a future. This allows future results to be passed from one active_function to another without waiting for the result to become ready. Since futures are constructible from their value types, the active_function can also take ordinary values not wrapped in futures as arguments. 

  2. bool expired() const;

    Calls the boost::slot::expired() query method on the slot this active_function was constructed from.