Question

I have roughly the following code. Could this be made nicer or more efficient? Perhaps using std::remove_if? Can you remove items from the map while traversing it? Can we avoid using the temporary map?

typedef std::map<Action, What> Actions; static Actions _actions;  bool expired(const Actions::value_type &action) {   return <something>; }  void bar(const Actions::value_type &action) {   // do some stuff }  void foo() {   // loop the actions finding expired items   Actions actions;   BOOST_FOREACH(Actions::value_type &action, _actions)   {     if (expired(action))       bar(action);     else       actions[action.first]=action.second;     }   }   actions.swap(_actions); } 

Answer 1

You could use erase(), but I don’t know how BOOST_FOREACH will handle the invalidated iterator. The documentation for map::erase states that only the erased iterator will be invalidated, the others should be OK. Here’s how I would restructure the inner loop:

Actions::iterator it = _actions.begin(); while (it != _actions.end()) {   if (expired(*it))   {     bar(*it);     Actions::iterator toerase = it;     ++it;     _actions.erase(toerase);   }   else     ++it; }