Strategy Pattern 🦆

Also Known As (Policy)

Definition: Define a family of algorithms, encapsulate each one, and make them interchangable. Strategy lets the algorithm vary independently from clients that use it.

This example is inspired from the book Head First: Design Patterns Second Edition

Strategy Pattern.cpp

#include <iostream>
#include <memory>
#include <vector>
#include <algorithm>
#include "MallardDuck.h"
#include "RubberDuck.h"
#include "DecoyDuck.h"

using namespace std;

int main() {
    vector<shared_ptr<Duck>> ducks;
    shared_ptr<Duck> mallard = make_shared<MallardDuck>();
    shared_ptr<Duck> rubber = make_shared<RubberDuck>();
    shared_ptr<Duck> decoy = make_shared<DecoyDuck>();    

    ducks.push_back(mallard);
    ducks.push_back(rubber);
    ducks.push_back(decoy);

    for_each(ducks.begin(), ducks.end(), [](shared_ptr<Duck> duck) {
        duck->display();
        duck->performFly();
        duck->performQuack();
    });

    return 0;
}

Console:

I'm a MallardDuck.
I can fly.
Quack!
I'm a RubberDuck.
I can't fly.
Squeak!
I'm a DecoyDuck.
I can't fly.
I make no sound!