Databases
StackOverflow2013
Postsdbo
POObserver pattern in c++
Body
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POObserver pattern in c++
    text
    copied!<p>I am having a bit of trouble with observer pattern I have a beverage class that uses decorator fine. I am trying to implement observer to let an observer( say a cell phone/text message) in this case know when there order is done. i wont include the beverage/decorator classes since they work fine.</p> <p>In main i was going to do something like this:</p> <pre><code>Subject mySubject = new Subject(); Observer myObserver1 = new Observer1(); Observer myObserver2 = new Observer2(); // register observers mySubject.Register(myObserver1); mySubject.Register(myObserver2); mySubject.Notify("message 1"); mySubject.Notify("message 2"); </code></pre> <p>I have a subject class, observer, phone behavior class and a cellhone1,cellphone2 classes..</p> <p>Here is the subject class</p> <pre><code>#ifndef _SUBJECT_ #define _SUBJECT_ //#include "Starbuzz.h" //#include "Starbuzz2.h" #include "Observer.h" #include &lt;list&gt; namespace CoffeeHouse { namespace Observers { class Subject { private: std::list&lt; Observer* &gt; observers; public: Subject(); ~Subject(); void Subject::Register(Observer observer) { //if (!observers.(observer)) //{ observers.insert(observer); } //} //void Unregister(Observer observer) //{ // if observer is in the list, remove //if (observers.Contains(observer)) //{ //observers.Remove(observer); //} //} void Notify(std::string message) { //need loop Observer observer; observer.update(message); } //} //} //void Subject::registerObserver( Observer* o ) { assert( o ); //_observers.push_front(o); //} //void Subject::removeObserver( Observer* o ) { assert( o ); // _observers.remove(o); //} //void Subject::notifyObservers() const { //for( std::list&lt; Observer* &gt;::iterator iterator = _observers.begin(); _observers.end() != iterator; ++iterator ) { //Observer* observer = *iterator; //observer-&gt;update(message); //} //} }; } // namespace Observer } #endif </code></pre> <p>Here is the observer class</p> <pre><code>#ifndef _OBSERVER_ #define _OBSERVER_ #include &lt;string&gt; namespace CoffeeHouse { namespace Observers { class Subject; class Observer { //public: virtual ~Observer() = 0; public: virtual void Update(std::string message) = 0; }; </code></pre> <p>here is the phone behavior class</p> <pre><code>#ifndef _PHONEBEHAVIOR_ #define _PHONEBEHAVIOR_ namespace CoffeeHouse { namespace Observer { class PhoneBehavior { public: virtual void Update() const = 0; }; protected: virtual ~PhoneBehavior() = 0 { }; }; } // namespace Observer } // </code></pre> <p>here is cellphone 1</p> <pre><code>#ifndef _CELLPHONE1_ #define _CELLPHONE1_ namespace CoffeeHouse { namespace Observer { include&lt;iostream&gt; class CellPhone1: public Observer, public PhoneBehavior { public: CellPhone1(); ~CellPhone1(); virtual void Update(std::string message) { std::cout &lt;&lt; "CellPhone1: " &lt;&lt; message; } }; } // namespace Observer } // #endif </code></pre> <p>here re the errors i am getting..</p> <pre><code>error C2259: 'CoffeeHouse::Observers::Observer' : cannot instantiate abstract class 1&gt; due to following members: 1&gt; 'void CoffeeHouse::Observers::Observer::update(std::string)' : is abstract see declaration of 'CoffeeHouse::Observers::Observer::update' error C2661: 'std::list&lt;_Ty&gt;::insert' : no overloaded function takes 1 arguments with[_Ty=CoffeeHouse::Observers::Observer * error C2259: 'CoffeeHouse::Observers::Observer' : cannot instantiate abstract class due to following members: 'void CoffeeHouse::Observers::Observer::update(std::string)' : is abstract observer.h(15) : see declaration of 'CoffeeHouse::Observers::Observer::update </code></pre> <p>When i click on error "cannot instantiate abstract class" it takes me to:</p> <pre><code>void Subject::Register(Observer observer) </code></pre> <p>I understand that Abstract classes are made such that they cannot be instantiated!</p> <p>How could i do an update then?? any suggestions of a better way?</p> <p>I appreciate any help! </p>
 

Querying!

 
Guidance
An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload