observer pattern - Event-driven design in C++ -

in event-driven application have common issue. suppose following class diagram:

i'm using observer pattern here. worker , workermanager lives in same thread. suppose sequence of actions:

1. worker calls listener class report result in middle of method
2. workermanager (which listener of worker) decides delete/modify worker class
3. worker continue execution of method, being removed of modified. programmer must consider these situations, , complicated , error-prone.

in code might that:

// in worker.cpp  void worker::somemethod() {     ...     listener_->onworkdone(this); // removed here listener     workdone_ = true; // memory corruption     ... }   // in worker_manager.cpp  void workermanager::onworkerworkdone(worker* worker) {     removeworker(worker); } 

how can modified:

// in worker.cpp  void worker::dosomework() {     workdone = false;     ... }  void worker::somemethod() {     ...     listener_->onworkdone(this); // sets workdone false here dosomework()     workdone_ = true; // somemethod doesn't aware of     ... }   // in worker_manager.cpp  void workermanager::onworkerworkdone(worker* worker) {     worker->dosomework(); // work } 

now see these solutions problem:

• set code style guide listener class must called last. quite fragile , error prone solution.
• made sort of qt queued connections.

qt queued connections made on meta-object system , way project. need simpler tool allow me defer listener callbacks in thread's event loop.

i believe issue common in event-driven design. can see examples of how can handled?