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Subject

Namespace: UTILSLIB  ·  Library: Utilities Library

#include <utils/observerpattern.h>

class UTILSLIB::Subject

DECLARE BASE CLASS SUBJECT.

The Subject class provides the base class of every subject of the observer design pattern.

src/examples/ex_utils/main.cpp
// A subject notifies every attached observer; observers pull the state they need
class Counter : public Subject
{
public:
    void increment()
    {
        ++m_value;
        notify();
    }
    int value() const
    {
        return m_value;
    }

private:
    int m_value = 0;
};

class LastSeen : public IObserver
{
public:
    void update(Subject* pSubject) override
    {
        m_seen = static_cast<Counter*>(pSubject)->value();
    }
    int seen() const
    {
        return m_seen;
    }

private:
    int m_seen = -1;
};

Inheritance​

Public Methods​

~Subject()​

Destroys the Subject.

attach(pObserver)​

Attaches an observer to the subject.

Parameters:

  • pObserver : *IObserver ** pointer to the observer which should be attached to the subject.

detach(pObserver)​

Detaches an observer of the subject.

Parameters:

  • pObserver : *IObserver ** pointer to the observer which should be detached of the subject.

notify()​

Notifies all attached servers by calling there update method.

Is used when subject has updates to provide. This method is enabled when nothifiedEnabled is true.

observers()​

Returns attached observers.

Returns:

  • t_Observers & — attached observers.

observerNumDebug()​

Returns attached observers.

Returns:

  • int — attached observers. Returns number of attached observers.

Example​

Used in examples​

ex_utils​

Utilities library: buffers, observers, logging, file formats, montages, layouts and reports.

src/examples/ex_utils/main.cpp, line 79
// A subject notifies every attached observer; observers pull the state they need
class Counter : public Subject
{
public:
    void increment()
    {
        ++m_value;
        notify();
    }
    int value() const
    {
        return m_value;
    }

Authors of this file​