c++ - Get Singleton of class that WILL be included -

i have classes:

activity, activitymanager (that extends activity).

i have 1 method in activity, gets singleton object of activitymanager.

after while, saw got "live without life" paradox, activitymanager "created" compiler, after activity is. so, how do sort of stuff?

i mean, how can class of object extended first one?

i don't know how put on google, so, me please! thanks

edit

simplified activity

class activity { public:     void start(); };  void activity::start(void){     // start current activity on activitymanager stack     activitymanager *am;     = activitymanager::getinstance();     am->start(this); } 

simplified activitymanager:

class activitymanager: public activity { private:     // singleton object     static activitymanager *singleton;  public:     // singleton method return defauld object instance     static activitymanager* getinstance(void);      // overload method, used run others activityes     void start(activity& activity);  };  // singleton method return default activitymanager object instance activitymanager* activitymanager::getinstance(){     if(!singleton) singleton = new activitymanager();      return singleton; }  // function called on request start new activity void activitymanager::start(activity& activity){ } 

i think composite pattern (http://en.wikipedia.org/wiki/composite_pattern) better needs.

it variation (naming bit screwed in terms of pattern, more code way):

class activity {     public:         virtual ~activity();          virtual void start();         virtual void add(activity*);         virtual void remove(activity*);      private:         activity(); }    class activitymanager : activity {     public:         concreteactivity();         ~concreteactivity();          void start();         void add(activity*);         void remove(activity*);      private:         list<activity*> _activities; }  void activitymanager::start() {     list<activity*>::const_iterator concreteactivity;      for(concreteactivity = _activities.begin(), concreteactivity != _activities.end(); ++concreteactivity)     {         *concreteactivity->start();     } }  void activitymanager::add(activity* newactivity) {     _activities.push_back(newactivity); }  void activitymanager::remove(activity* activitytodelete) {     _activities.remove(activitytodelete); }     class someactivity : activity {      public:          someactivity();          ~someactivity();           void start(); }  class otheractivity : activity {      public:          otheractivity();          ~otheractivity();           void start(); } 

and example of usage:

activitymanager* manager = new activitymanager();  someactivity* activity_one = new someactivity(); otheractivity* activity_two = new otheractivity();  manager->add(activity_one); manager->add(activity_two); manager->start(); 

and still can make activitymanager singleton, if want. without additional info on project, can't think of better way.