A message wrapped to be used as type of argument for event handlers. More...

#include <mhood.hpp>

Inheritance diagram for so_5::mhood_t< M >:

Private Types
using	base_type_t = details::actual_mhood_base_type< M >

Detailed Description

A message wrapped to be used as type of argument for event handlers.

Template Parameters

M	type of message or signal.

Note: This class provides different sets of methods in dependency of type M. If M is a type derived from so_5::message_t, then there will be the following methods for immutable message M:
const M * get() const;
const M * operator->() const;
const M & operator*() const;
so_5::intrusive_ptr_t< M > make_reference() const;
so_5::message_holder_t< M, Ownership > make_holder<Ownership>() const;
If M is a type derived from so_5::signal_t, then there will no be methods at all. It is because there is no actual message object for a signal. If M is user-type message then there will be the following methods for immutable message M:
const M * get() const;
const M * operator->() const;
const M & operator*() const;
so_5::intrusive_ptr_t< so_5::user_type_message_t<M> > make_reference() const;
so_5::message_holder_t< M, Ownership > make_holder<Ownership>() const;
For mutable message M there will be the following methods is M is derived from so_5::message_t:
M * get();
M * operator->();
M & operator*();
so_5::intrusive_ptr_t< M > make_reference();
so_5::message_holder_t< M, Ownership > make_holder<Ownership>();
If mutable message M is not derived from so_5::message_t then there will be the following methods:
M * get();
M * operator->();
M & operator*();
so_5::intrusive_ptr_t< so_5::user_type_message_t<M> > make_reference();
so_5::message_holder_t< M, Ownership > make_holder<Ownership>();; Method make_holder() uses so_5::message_ownership_t::autodetected by default.

Attention: Methods make_reference() for mhood_t<mutable_msg<M>> will leave mhood object in nullptr state. It means that mhood must not be used after calling make_reference().; Methods make_holder() for mhood_t<mutable_msg<M>> will leave the mhood object empty always. Regardless of Ownership parameter. Methods make_holder() for mhood_t<M> and mhood_t<immutable_msg<M>> will leave value for mhood object regardless of Ownership parameter. For example:
class demo : public agent_t {
void on_immutable_msg(mhood_t<some_msg> cmd) {
auto unique_holder = cmd.make_holder<so_5::message_ownership_t::unique>();
auto v = cmd->some_value(); // cmd still has its value.
...
}
...
void on_mutable_msg(mhood_t< mutable_msg<another_msg> > cmd) {
auto shared_holder = cmd.make_holder<so_5::message_ownership_t::shared>();
// Now cmd is empty!
auto v = cmd->some_value(); // THIS IS UB!
}
};

Note: Class mhood_t can be used for redirection of messages of user types. For example (since v.5.5.19):
class redirector : public so_5::agent_t
{
...
void some_event( mhood_t< std::string > evt ) {
// Redirection of message to the different mbox.
so_5::send(m_another_mbox, evt);
}
};
If mhood_t<mutable_msg<M>> is used then a redirection must be done this way:
class redirector : public so_5::agent_t
{
...
void some_event( mhood_t< mutable_msg<std::string> > evt ) {
// Redirection of message to the different mbox.
so_5::send(m_another_mbox, std::move(evt));
// NOTE: evt is nullptr at this point. It must not be used anymore.
}
};