Re: MVC in C++

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Date: Tue, 1 Mar 2005 14:55:46 +0100

Here is another try to program a minimalist Model-View-Controller implementation
in C++. Thanks to Alex Kaye and others for useful comments on the previous
version. I want very much to have this code reviewed again, specially the
/design/.

When you run the program, you get this prompt:

________________________
Type t to edit Title, v to edit Version, c to edit Credits. Type q to quit.
>>(cursor waiting for input)

I do not know how to implement the following:

When I type t, for instance, I want the Model::Title_Caption to appear on the
screen, like this:

________________________
Type t to edit Title, v to edit Version, c to edit Credits. Type q to quit.
>>t
Title: (cursor waiting)

How can I get TitleView to show this part of Model? Via Model? With an Event?
I'm out of my wits.

#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
{

 //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);
 }
};

//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();}
};

//struct TitleView, specialized Observer
struct TitleView:Observer
{

 //update
 void update(void*a)
 {
  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;

 //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
{

 //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;
}

• Previous message: Jason Jones: "Smalltalk Solutions Coding Contest"
• Next in thread: Daniel T.: "Re: MVC in C++"
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• Reply: alex99_at_medcentral.com.au: "Re: MVC in C++"
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