cpp_tests/t103_observer_pattern.cpp at master · s-kramer/cpp_tests · GitHub

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#include <iostream>

#include <vector>

using namespace std;

class Subject {

// 1. "independent" functionality

vector < class Observer * > views; // 3. Coupled only to "interface"

int value;

public:

void attach(Observer *obs) {

views.push_back(obs);

}

void setVal(int val) {

value = val;

notify();

}

int getVal() {

return value;

}

void notify();

};

class Observer {

// 2. "dependent" functionality

Subject *model;

int denom;

public:

Observer(Subject *mod, int div) {

model = mod;

denom = div;

// 4. Observers register themselves with the Subject

model->attach(this);

}

virtual void update() = 0;

protected:

Subject *getSubject() {

return model;

}

int getDivisor() {

return denom;

}

};

void Subject::notify() {

// 5. Publisher broadcasts

for (int i = 0; i < views.size(); i++)

views[i]->update();

}

class DivObserver: public Observer {

public:

DivObserver(Subject *mod, int div): Observer(mod, div){}

void update() {

// 6. "Pull" information of interest

int v = getSubject()->getVal(), d = getDivisor();

cout << v << " div " << d << " is " << v / d << '\n';

}

};

class ModObserver: public Observer {

public:

ModObserver(Subject *mod, int div): Observer(mod, div){}

void update() {

int v = getSubject()->getVal(), d = getDivisor();

cout << v << " mod " << d << " is " << v % d << '\n';

}

};

int main() {

Subject subj;

DivObserver divObs1(&subj, 4); // 7. Client configures the number and

DivObserver divObs2(&subj, 3); // type of Observers

ModObserver modObs3(&subj, 3);

subj.setVal(14);

}

cpp_tests/t103_observer_pattern.cpp at master · s-kramer/cpp_tests · GitHub

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