#include<iostream> #include<vector>//get namespace related stuff using std::cin; using std::cout; using std::endl; using std::flush; using std::string; using std::vector;  //struct Observer, modeled after java.utils.Observer struct Observer /*  * AK: This could be a template (C++) or generic (Java 5),  * however the original Smalltalk MVC didn‘t do that.  */ {    //update    virtual void update(void*)=0; };   //struct Observable, modeled after java.utils.Observable struct Observable {    //observers    vector<Observer*>observers;       //addObserver    void addObserver(Observer*a){observers.push_back(a);}       //notifyObservers    void notifyObservers()    {     for (vector<Observer*>::const_iterator observer_iterator=observers.begin();observer_iterator!=observers.end();observer_iterator++)      (*observer_iterator)->update(this);    }     /*   AK: If you had a method which takes an extra "ARG" argument like this   notifyObservers(void* ARG), you can pass that arg to each Observer via   the call (*observer_iterator)->update(this,ARG);       This can significantly increase your View‘s reusablity down the track.   I‘ll explain why below in the View.   */};    //struct Model, contains string-data and methods to set and get the data struct Model:Observable {    //data members title_caption, version_caption, credits_caption    string title_caption;    string version_caption;    string credits_caption;       //data members title, version, credits    string title;    string version;    string credits;       //constructor    Model() :     title_caption("Title: "),     version_caption("Version: "),     credits_caption("Credits: "),     title("Simple Model-View-Controller Implementation"),     version("0.2"),     credits("(put your name here)")     { }       //getCredits_Caption, getTitle_Caption, getVersion_Caption    string getCredits_Caption(){return credits_caption;}    string getTitle_Caption(){return title_caption;}    string getVersion_Caption(){return version_caption;}       //getCredits, getTitle, getVersion    string getCredits(){return credits;}    string getTitle(){return title;}    string getVersion(){return version;}       //setCredits, setTitle, setVersion    void setCredits(string a){credits=a;notifyObservers();}    void setTitle(string a){title=a;notifyObservers();}    void setVersion(string a){version=a;notifyObservers();}   /*    * AK notifyObservers(a) for credit, title and version.    * All as per discussion in View and Observer *     */ };/* AK: Great stuff ;-) This satisfies a major principle of the MVC architecture, the separation of model and view.The model now has NO View material in it, this model can now be used in other applications. You can use it with command line apps (batch, testing, reports, ...), web, gui, etc.Mind you "MVC with Passive Model" is a variation of MVC where the model doesn‘t get even involved with the Observer pattern.In that case the Controller would trigger a model update *and it* could also supply the latest info do the Views. This is a fairly common MVC variation, especially with we apps. */  //struct TitleView, specialized Observer struct TitleView:Observer { /*  * AK:  * I like to get a reference to the model via a constructor to avoid  * a static_cast in update and to avoid creating zombie objects.  *  * A zombie object is instantiated but is unusable because it  * is missing vital elements. Dangerous. Getting model via the  * constructor solves this problem. Model model;  // Cons.  TitleView (Model* m) ....RE-USABILITY. Some views are better off working with the full Model, yet others are better off being dumber.I like to have two kinds of Views. Those that work with full Model (A) and those that only work with a limited more abstract data type (B).Type A. Complex application specific views are better off getting the full model, they can then just pick and choose what they need from the full model without missing something all the time. Convenient.Type B. These only require abstract or generic data types.Consider a PieChartView, it doesn‘t really need to know about the full Model of a particular application, it can get by with just float *values[] or vector<float>;By avoiding Model you can then reuse PieChartView in other applications with different models.For this to be possible you must use the 2 argument version of notifyObservers. See comments on Observer class.See my Java example NameView. That view only knows about a String, not the full Model. */   //update    void update(void*a)   /*    *AK:void update(void*a, void*arg) is often better. As per discussion   above.    */    {    cout<<static_cast<Model*>(a)->getTitle_Caption();    cout<<static_cast<Model*>(a)->getTitle();    cout<<endl;    } };    //struct VersionView, specialized Observer struct VersionView:Observer {   //update  void update(void*a)  {  cout<<static_cast<Model*>(a)->getVersion_Caption();  cout<<static_cast<Model*>(a)->getVersion();  cout<<endl;  } };    //struct CreditsView, specialized Observer struct CreditsView:Observer {   //update  void update(void*a)  {  cout<<static_cast<Model*>(a)->getCredits_Caption();  cout<<static_cast<Model*>(a)->getCredits();  cout<<endl;  } };    //struct Views, pack all Observers together in yet another Observer struct Views:Observer {  //data members titleview, versionview, creditsview  TitleView titleview;  VersionView versionview;  CreditsView creditsview; /*  * AK:  * Views are often hierarchical and composed of other Views. See Composite pattern.  * vector<View*> views;  *  * Views often manage (create and own) a Controller.  *  * Views may include their own Controller code (Delegate).  * */  //setModel  void setModel(Observable&a)  {  a.addObserver(&titleview);  a.addObserver(&versionview);  a.addObserver(&creditsview);  a.addObserver(this);  }   //update  void update(void*a)  {  cout<<"_____________________________";  cout<<"\nType t to edit Title, ";  cout<<"v to edit Version, ";  cout<<"c to edit Credits. ";  cout<<"Type q to quit./n>>";  } };    //struct Controller, wait for keystroke and change Model  struct Controller /*  * AK: Controller can also be an Observer.  *  * There is much to say about Controller but IMHO we should defer  * that to another version.  */ {    //data member model    Model*model;       //setModel    void setModel(Model&a){model=&a;}       //MessageLoop    void MessageLoop()    {     char c=‘ ‘;     string s;     while(c!=‘q‘)     {       cin>>c;       cin.ignore(256,‘\n‘);       cin.clear();       switch(c)       {        case ‘c‘:        case ‘t‘:        case ‘v‘:        getline(cin,s);        break;       }       switch(c)       {        case ‘c‘:model->setCredits(s);break;        case ‘t‘:model->setTitle(s);break;        case ‘v‘:model->setVersion(s);break;       }     }    } };    //struct Application, get Model, Views and Controller together struct Application {     //data member model    Model model;       //data member views    Views views;       //data member controller    Controller controller;       //constructor    Application()    {    views.setModel(model);    controller.setModel(model);    model.notifyObservers();    }       //run    void run(){controller.MessageLoop();} };    //main int main() {   Application().run();   return 0; }