Menu (any default style ? )

I am currently practice to upgrade my (novice) skills and I want to know if there any default/universal way of coding the menu choices. For example:

1. Wake up
2. Sleep
3. Sit Down
4. Take Home
Select you choice:

I thought of this:

Code:

---

#include <iostream>

using namespace std;

enum CHOICE  {
    Wake = 1,
    Bath,
    Toilet,
    Hack,
    Quit  };

// Function Definition and Prototype

int DoMenu()
{
    int choice;
   
    cout << endl << endl;
    cout << " ***** Menu ***** " <<endl;
    cout << "(1) Wake me up when project ends" << endl;
    cout << "(2) GOTO Bathroom" << endl;
    cout << "(3) fflussh(toilet)" << endl;
    cout << "(4) Hack the kernel" << endl;
    cout << "(5) Quit" << endl;
   
    cin >> choice;
    return choice;
}

int main()
{
    int choice;
    bool fQuit = false;
   
    while (!fQuit)
    {
          choice = DoMenu();
         
          if ( choice < Wake || choice > Quit )
          {
              cout << "Wrong pal";
              cout << endl << endl;
             
              continue;
          }
         
          switch(choice)
          {
                        case Wake:
                            cout << "Drinsane!!! " << endl;
                            break;
                        case Bath:
                            cout << "Please wait while bathing ... " << endl;
                            cout << "You smell sehr gut" << endl;
                            break;
                        case Toilet:
                            break;
                        case Hack:
                            break;
                        case Quit:
                            fQuit = true;
                            cout << "\nExiting .... " << endl << endl;
                            break;
                        default:
                                fQuit = true;
                                cout << "\nExiting .... " << endl << endl;
                                break;
          }
    }
    system("PAUSE");
    return 0;
}

---

ButI think that the above source code is strange a bit. Is there any particular style that you, experienced programmers use ?

In the meantime I thought this:

Code:

---

#include <iostream>

using namespace std;

enum CHOICE  {
    Wake = 1,
    Bath,
    Toilet,
    Hack,
    Quit  };

// Function Definition and Prototype

void ShowMenu()
{
   
    cout << endl << endl;
    cout << " ***** Menu ***** " <<endl;
    cout << "(1) Wake me up when project ends" << endl;
    cout << "(2) GOTO Bathroom" << endl;
    cout << "(3) fflussh(toilet)" << endl;
    cout << "(4) Hack the kernel" << endl;
    cout << "(5) Quit" << endl;
}

void InputCheck(int choice)
{
    while ( choice < Wake || choice > Quit )
    {
          cout << "/nWrong! Retry ..." << endl;
          cout << "Select you choice (in number) :";
      cin >> choice;
    }
}

int main()
{
    int choice;
    bool fQuit = false;
   
          ShowMenu();
          cout << "Select you choice (in number) :";
          cin >> choice;
          InputCheck(choice);
         
                   
          switch(choice)
          {
                        case Wake:
                            cout << "Drinsane!!! " << endl;
                            break;
                        case Bath:
                            cout << "Please wait while bathing ... " << endl;
                            cout << "You smell sehr gut" << endl;
                            break;
                        case Toilet:
                            break;
                        case Hack:
                            break;
                        case Quit:
                            fQuit = true;
                            cout << "\nExiting .... " << endl << endl;
                            break;
                        default:
                                fQuit = true;
                                cout << "\nExiting .... " << endl << endl;
                                break;
          }
    system("PAUSE");
    return 0;
}

---

Well I think that is best:

Code:

---

#include <iostream>

using namespace std;

enum CHOICE  {
    Wake = 1,
    Bath,
    Toilet,
    Hack,
    Quit  };

// Function Definition and Prototype

int DoMenu()
{
    int choice;
   
    cout << endl << endl;
    cout << " ***** Menu ***** " <<endl;
    cout << "(1) Wake me up when project ends" << endl;
    cout << "(2) GOTO Bathroom" << endl;
    cout << "(3) fflussh(toilet)" << endl;
    cout << "(4) Hack the kernel" << endl;
    cout << "(5) Quit" << endl;
   
    cin >> choice;
    return choice;
}

int main()
{
    int choice;
    bool fQuit = false;
   
    while (!fQuit)
    {
          char  reSelect;
          choice = DoMenu();
     
          switch(choice)
          {
                        case Wake:
                            cout << "Drinsane!!! " << endl;
                            break;
                        case Bath:
                            cout << "Please wait while bathing ... " << endl;
                            cout << "You smell sehr gut" << endl;
                            break;
                        case Toilet:
                            break;
                        case Hack:
                            break;
                        case Quit:
                            fQuit = true;
                            cout << "\nExiting .... " << endl << endl;
                            break;
                        default:
                                fQuit = true;
                                cout << "\nExiting .... " << endl << endl;
                                break;
          }
         
          if (fQuit == false)
          {
                    cout << "\n\t\tDo you want to select again ? (Y/N):";
                    cin >> reSelect;
         
                    if ( reSelect = 'Y' )
                    {
                        continue;
                    }
          }
}       
         
    system("PAUSE");
    return 0;
}

---

Comments in the code in red!

Quote:

---

Originally Posted by BlackSlash12

Code:

---

...
                        case Quit:
                            fQuit = true;
                            cout << "\nExiting .... " << endl << endl;
                            break;
                        default:
So, if the poor user presses any other number, it automatically quits the application
                                fQuit = true;
                                cout << "\nExiting .... " << endl << endl;
                                break;
          }
         
          if (fQuit == false)
          {
                    cout << "\n\t\tDo you want to select again ? (Y/N):";
                    cin >> reSelect;
       
 
                  if ( reSelect = 'Y' )  // Assigning reSelect with 'Y' will always be true, as 'Y' is not 0!
                    {
What's te purpose of this bit then? Do you actually understand what this does?
                        continue;
                    }
Assuming the user pressed "N", what is supposed to happen? [And assuming your assignment is changed to a test for equality]
          }
}       
         
    system("PAUSE");
    return 0;
}

---

---

--
Mats

So...what to do ? Could you fix it or post your code-design style ?

Quote:

---

Originally Posted by BlackSlash12

So...what to do ? Could you fix it or post your code-design style ?

---

Well, if you want the user to quit due to selecting an invalid choice, that's your choice - but I prefer applications that let me be a bit clumsy - do you ever hit the wrong key?

As to your use of assignment instead of test for equality, I would prefer this:

Code:

---

                    if ( 'Y' == reSelect )
                    {
                        continue;
                    }

---

But of course, there's no reason to do any of it, because it makes no difference - continue is only useful in a loop if there's something else to do after the continue statement. In this case, there's just closing braces between this point and the end of the while-loop, so the whole if-statement is pointless.

Of course, the other unanswered question is what you want to do if N is pressed - is that supposed to do something, or is Y and N equivalent - if so, why do you ask the user to enter Y or N? [And of course, what happens if it's neither?]

--
Mats

I want to display the menu choices and then let the user to select one. That's ok.

Afterwards I wan to create a input check.

Code:

---

while (choice > 5 || choice <0)
{
      cout << "You wrong";
      cout << "Retype: ";
      cin >> choice;
}

---

Is this code block, ok ?

Quote:

---

Originally Posted by BlackSlash12

I want to display the menu choices and then let the user to select one. That's ok.

Afterwards I wan to create a input check.

Code:

---

while (choice > 5 || choice <0)
{
      cout << "You wrong";
      cout << "Retype: ";
      cin >> choice;
}

---

Is this code block, ok ?

---

Yes, except you may want to use the enums instead of numbers - otherwise, what's the point of using enums in the first place?

edit: And by the way, the code you show here will allow zero as a valid choice, which isn't valid. Another reason to use the enum.

--
Mats

You right!Fixed but what about the loop ? I want the opportunity to reselect again (if pressed y) or exit (if pressed n).

Code:

---

#include <iostream>

using namespace std;

enum CHOICE  {
    Wake = 1,
    Bath,
    Toilet,
    Hack,
    Quit  };

// Function Definition and Prototype

int DoMenu()
{
    int choice;
   
    cout << endl << endl;
    cout << " ***** Menu ***** " <<endl;
    cout << "(1) Wake me up when project ends" << endl;
    cout << "(2) GOTO Bathroom" << endl;
    cout << "(3) fflussh(toilet)" << endl;
    cout << "(4) Hack the kernel" << endl;
    cout << "(5) Quit" << endl;
   
    cin >> choice;
    while (choice > Quit || choice < Wake)
{
      cout << "You wrong! ";
      cout << "Retype: ";
      cin >> choice;
}
    return choice;
}

int main()
{
    int choice;
    bool fQuit = false;
   
    while (!fQuit)
    {
          char  reSelect;
          choice = DoMenu();
     
          switch(choice)
          {
                        case Wake:
                            cout << "Drinsane!!! " << endl;
                            break;
                        case Bath:
                            cout << "Please wait while bathing ... " << endl;
                            cout << "You smell sehr gut" << endl;
                            break;
                        case Toilet:
                            break;
                        case Hack:
                            break;
                        case Quit:
                            fQuit = true;
                            cout << "\nExiting .... " << endl << endl;
                            break;
                        default:
                                fQuit = true;
                                cout << "\nExiting .... " << endl << endl;
                                break;
          }
         
          cout << "Do you want to select another one ?  (y/n) :";
          cin >> reSelect;
       
        /// What now ???             
         
         
}       
         
    system("PAUSE");
    return 0;
}

---

What do you think it should do to reselect?

I don't really understand why you want to have a yes-no question there, rather than just go back to the menu - there is a menu choice to exit, right? So why have another question that asks if you want to exit or continue?

--
Mats

For example if I select 3 a particular message is printed. How can I come back to the menu ? I do not know .... so I invested y/n.

I think I made it!

Code:

---

#include <iostream>

using namespace std;

enum CHOICE  {
    Wake = 1,
    Bath,
    Toilet,
    Hack,
    Quit  };

// Function Definition and Prototype

int DoMenu()
{
    int choice;
   
    cout << endl << endl;
    cout << " ***** Menu ***** " <<endl;
    cout << "(1) Wake me up when project ends" << endl;
    cout << "(2) GOTO Bathroom" << endl;
    cout << "(3) fflussh(toilet)" << endl;
    cout << "(4) Hack the kernel" << endl;
    cout << "(5) Quit" << endl;
   
    cout << "Please select :";
    cin >> choice;
    while (choice > Quit || choice < Wake)
{
      cout << "You wrong! ";
      cout << "Retype: ";
      cin >> choice;
}
    return choice;
}

int main()
{
    int choice;
    bool fQuit = false;
   
    while (!fQuit)
    {
          char  reSelect;
          choice = DoMenu();
     
          switch(choice)
          {
                        case Wake:
                            cout << "Drinsane!!! " << endl;
                            break;
                        case Bath:
                            cout << "Please wait while bathing ... " << endl;
                            cout << "You smell sehr gut" << endl;
                            break;
                        case Toilet:
                            break;
                        case Hack:
                            break;
                        case Quit:
                            fQuit = true;
                            cout << "\nExiting .... " << endl << endl;
                            break;
                        default:
                                fQuit = true;
                            cout << "\nExiting .... " << endl << endl;
                            break;
          }
         
          if (choice != Quit )
          {
                    cout << "Do you want to select another one ?  (y/n) :";
                    cin >> reSelect;
                    while (reSelect != 'y' && reSelect != 'n')
                    {
                          cout << "You wrong! Type 'y' or 'n' :";
                          cin >> reSelect;
                    }
                    if (reSelect == 'n')
                    {
                                cout << "\nExiting .... " << endl << endl; 
                                break;
                    }
          }
                         
       
        /// What now ???             
         
         
}       
         
    system("PAUSE");
    return 0;
}

---

Right isn't it ? If you wish you could post your way (without y/n).

Sorry for double post, I just found what you mean.

Code:

---

#include <iostream>

using namespace std;

enum CHOICE  {
    Wake = 1,
    Bath,
    Toilet,
    Hack,
    Quit  };

// Function Definition and Prototype

int DoMenu()
{
    int choice;
   
    cout << endl << endl;
    cout << " ***** Menu ***** " <<endl;
    cout << "(1) Wake me up when project ends" << endl;
    cout << "(2) GOTO Bathroom" << endl;
    cout << "(3) fflussh(toilet)" << endl;
    cout << "(4) Hack the kernel" << endl;
    cout << "(5) Quit" << endl;
   
    cout << "Please select :";
    cin >> choice;
    while (choice > Quit || choice < Wake)
{
      cout << "You wrong! ";
      cout << "Retype: ";
      cin >> choice;
}
    return choice;
}

int main()
{
    int choice;
    bool fQuit = false;
   
    while (!fQuit)
    {
          char  reSelect;
          choice = DoMenu();
     
          switch(choice)
          {
                        case Wake:
                            cout << "Drinsane!!! " << endl;
                            break;
                        case Bath:
                            cout << "Please wait while bathing ... " << endl;
                            cout << "You smell sehr gut" << endl;
                            break;
                        case Toilet:
                            break;
                        case Hack:
                            break;
                        case Quit:
                            fQuit = true;
                            cout << "\nExiting .... " << endl << endl;
                            break;
                        default:
                                fQuit = true;
                            cout << "\nExiting .... " << endl << endl;
                            break;
          }
         
          if (choice != Quit )
          {
                    continue;
          }
                         
       
        /// What now ???             
         
         
}       
         
    system("PAUSE");
    return 0;
}

---

Is this ?

I still don't understand the reason for your "if (choice != Quit) continue;" - it's not needed, the while-loop will continue anyways, until your end-condtion (fQuit) becomes true.

--
Mats

You right! Do you prefer using enum or not ?

You should clear the error flags on std::cin after a failed read (e.g., the user entered letters instead of an integer) and ignore what remains on the buffer otherwise you risk an infinite loop.

Quote:

---

Do you prefer using enum or not ?

---

I think they are fine for what you want to do.

As an alternative, you could try implementing the menu via callback functions. You could create a menu item class that stores the description of the menu item and a function pointer to the function that you want to call if the user selects that option. A menu class could then store a list of menu items and perhaps a heading for the menu. The menu class could have a member function that displays the menu (in a loop, automatically numbering the menu items), handles user input, and then runs the callback function of the selected menu item.

Once you have written these two classes, creating a menu would just involve creating a menu object and adding menu item objects to it. The tradeoff is that this is more initial work in implementing these two classes and you have to create a callback function for each menu option (but for a reasonably complex option, you would write a function for that anyway). On the other hand, you can just create menu objects in those functions so as to have sub-menus.

Quote:

---

You should clear the error flags on std::cin after a failed read (e.g., the user entered letters instead of an integer) and ignore what remains on the buffer otherwise you risk an infinite loop.

---

How can I do this ?

Quote:

---

As an alternative, you could try implementing the menu via callback functions. You could create a menu item class that stores the description of the menu item and a function pointer to the function that you want to call if the user selects that option. A menu class could then store a list of menu items and perhaps a heading for the menu. The menu class could have a member function that displays the menu (in a loop, automatically numbering the menu items), handles user input, and then runs the callback function of the selected menu item.

Once you have written these two classes, creating a menu would just involve creating a menu object and adding menu item objects to it. The tradeoff is that this is more initial work in implementing these two classes and you have to create a callback function for each menu option (but for a reasonably complex option, you would write a function for that anyway). On the other hand, you can just create menu objects in those functions so as to have sub-menus.

---

This sounds very interesting. Although I am not used of pointers (it's the next chapter on my C++ book) I would like to see a source code that does this implementation. Could you or anyone else post it here ?

Clearing input when failed:
http://faq.cprogramming.com/cgi-bin/...&id=1043284392

I've never written C++ classes to support menus, but it shouldn't be hard to do. Perhaps something like this:

Code:

---

#include <iostream>
#include <string>


class menucontext {
public:
  bool fquit;
  menucontext() : fquit(false) { };
  ~menucontext() {};
};

typedef void (*menufunc)(menucontext &ctxt);


class menuitem {
private:
  std::string  descr;
  char          choice;
  menufunc      func;
public:
  menuitem(const std::string &s, char c, menufunc f):
    descr(s), choice(c), func(f)
  {
  };
  ~menuitem() {
  };
  void print() {
    std::cout << choice << ": " << descr << std::endl;
  };
  void domenu(menucontext &ctxt) {
    func(ctxt);
  };
  bool isChoice(char c) {
    return (c == choice);
  }
};

 

class menu {
private:
  struct menunode {
    menunode *next;
    menuitem *item;
  };
  menunode *head;
  menunode *tail;
public:
  menu() : head(0), tail(0) {
  }
  ~menu() {
    menunode *p, *q;
    for(p = head; p; p = q) {
      q = p->next;
      delete p->item;
      delete p;
    }
  };
  void addmenu(std::string s, char c, menufunc f) {
    menunode *node = new menunode;
    node->item = new menuitem(s, c, f);
    node->next = 0;
    if (!head)
      head = tail = node;
    else {
      tail->next = node;
      tail = node;
    }
  };
  void choose(menucontext &ctxt) {
    char c;
    menunode *p;
    bool choosen = false;
    for(p = head; p; p = p->next) {
      p->item->print();
    }
    do {
      std::cin >> c;
      for(p = head; p; p = p->next) {
        if (p->item->isChoice(c)) {
          p->item->domenu(ctxt);
          choosen = true;
        }
      }
      if (!choosen)
        std::cout << "That wasn't a valid choice" << std::endl;
    } while(!choosen);
  };
};


void first(menucontext &ctxt)
{
  std::cout << "In first" << std::endl;
}

void quit(menucontext &ctxt)
{
  std::cout << "Quitting..." << std::endl;
  ctxt.fquit = true;
}


int main() {
  menu m;

  menucontext ctxt;
  m.addmenu("First menu", '1', first);
  m.addmenu("QUit",      'q', quit);

  while(!ctxt.fquit)
    m.choose(ctxt);
  return 0;
}

---

[That got a lot longer than I expected.]

--
Mats

By the way, I guess it's a good idea to use some STL to make the list of menuitems, e.g. a list or vector.

Code:

---

#include <list>
...
class menuitem {
private:
  std::string  descr;
  char          choice;
  menufunc      func;
public:
  menuitem(const std::string &s, char c, menufunc f):
    descr(s), choice(c), func(f)
  {
  };
  ~menuitem() {
  };
  void print() const {
    std::cout << choice << ": " << descr << std::endl;
  };
  void domenu(menucontext &ctxt) const {
    func(ctxt);
  };
  bool isChoice(char c) const {
    return (c == choice);
  }
};

 

class menu {
private:
  std::list<menuitem> menuitems;
public:
  menu() {
  }
  ~menu() {
    menuitems.clear();
  };
  void addmenu(std::string s, char c, menufunc f) {
    menuitems.push_back(menuitem(s, c, f));
  };
  void choose(menucontext &ctxt) {
    char c;
    std::list<menuitem>::const_iterator i;
    bool choosen = false;
    for(i = menuitems.begin(); i != menuitems.end(); i++) {
      i->print();
    }
    do {
      std::cin >> c;
      for(i = menuitems.begin(); i != menuitems.end(); i++) {
        if (i->isChoice(c)) {
          i->domenu(ctxt);
          choosen = true;
        }
      }
      if (!choosen)
        std::cout << "That wasn't a valid choice" << std::endl;
    } while(!choosen);
  };
};

---

The above is the changed code, marked in red.

--
Mats

Pretty cool! I think that I have not the skills to write something like this but I will (someday:P).

in the link you gave me there is :

Code:

---

#include <iostream>
#include <cstdio>

using std::cin;
using std::cout;
using std::endl;

int main(void)
{
  int ch;
  char buf[BUFSIZ];
   
  cout <<"Flushing input" <<endl;
 
  while ((ch = cin.get()) != '\n' && ch != EOF);
 
  cout <<"Enter some text: ";
  cout.flush();
 
  if (cin.getline(buf, sizeof(buf)))
  {
    cout <<"You entered: " <<buf <<endl;
  }

  return 0;
}

/*
 * Program output:
 *
 Flushing input
 blah blah blah blah
 Enter some text: hello there
 You entered: hello there
 *
 */

---

I didn't understand very well. Should I use
cout.flush();
under every cout command ?

Am I forced to use the strange if conditions including EOF ? WTF ?

This line is the one that does the actual "eating of any garbage in the inptut".

Code:

---

while ((ch = cin.get()) != '\n' && ch != EOF);

---

The purpose is mainly to avoid a whole stream of "invalid input" when you've entered "jkdfhukadshfjghawerihfj" because the cat decided to walk on the keyboard (or my 8m old daughter decided "to help daddy do typing"). When using numeric input (as you do when you read an enum), the input could get into a "stuck" state, in which case you also want to use cout.clear() to clear the error flag that has been set.

And yes, it's a good idea to check for EOF - if you don't, things will sooner or later go into an infinite loop when reading something.

--
Mats

Could you edit my code with this additional stuff ? I am comfused with this "buf"... Sorry if bothering, man.

When you see that someone made the wrong choice, just insert that line I posted two posts ago - that will read anything "still waiting to be processed" up to the "enter".

--
Mats

Code:

---

#include <iostream>

using namespace std;

enum CHOICE  {
    Wake = 1,
    Bath,
    Toilet,
    Hack,
    Quit  };

// Function Definition and Prototype

int DoMenu()
{
    int choice;
   
    cout << endl << endl;
    cout << " ***** Menu ***** " <<endl;
    cout << "(1) Wake me up when project ends" << endl;
    cout << "(2) GOTO Bathroom" << endl;
    cout << "(3) fflussh(toilet)" << endl;
    cout << "(4) Hack the kernel" << endl;
    cout << "(5) Quit" << endl;
   
    cout << "Please select :";
    cin >> choice;
    cin.ignore(choice);
 while (choice > Quit || choice < Wake)
{
    while ((choice = cin.get()) != '\n' && ch != EOF);
      cout << "You wrong! ";
      cout << "Retype: ";
      cin >> choice;
}
    return choice;
}

int main()
{
    int choice;
    bool fQuit = false;
   
    while (!fQuit)
    {
          char  reSelect;
          choice = DoMenu();
     
          switch(choice)
          {
                        case Wake:
                            cout << "Drinsane!!! " << endl;
                            break;
                        case Bath:
                            cout << "Please wait while bathing ... " << endl;
                            cout << "You smell sehr gut" << endl;
                            break;
                        case Toilet:
                            break;
                        case Hack:
                            break;
                        case Quit:
                            fQuit = true;
                            cout << "\nExiting .... " << endl << endl;
                            break;
                        default:
                                fQuit = true;
                            cout << "\nExiting .... " << endl << endl;
                            break;
          }
       
 
         
}       
         
    system("PAUSE");
    return 0;
}

---

errors....

You haven't declared the variable ch.
You probably don't want to pass choice to cin.ignore();

The "reselect" variable in main is never used.

--
Mats

This block of code:

Code:

---

cout << "Please select :";
cin >> choice;
cin.ignore(choice);
while (choice > Quit || choice < Wake)
{
    while ((choice = cin.get()) != '\n' && ch != EOF);
    cout << "You wrong! ";
    cout << "Retype: ";
    cin >> choice;
}

---

Should be:

Code:

---

cout << "Please select :";
while (!(cin >> choice) || choice > Quit || choice < Wake)
{
    cin.clear();
    cin.ignore(numeric_limits<streamsize>::max(), '\n');
    cout << "You wrong! Retype: ";
}

---

While the read fails, or if the input is out of range, you inform the user of an error and request for more input. The cin.clear() clears the error flags after a failed read. The cin.ignore() removes remaining characters on the buffer up to and including the new line character. As far as I know, you do not need to worry about EOF here since the user has to press enter to enter input, thus placing a new line on the input buffer. The numeric_limits<streamsize>::max() returns the maximum size of a stream, but you need to #include <limits> to use it.