Design Patterns – Decorator – Code source simple en C++

Je lis toujours Head First Design Patterns. J’en suis au chapitre 3, page 79. Je m’attaque donc au Decorator en C++.

Ce que j’ai retenu

Plus tard, je vais mettre ici mes notes à propos du Design Patterns en question. Là il n’y a rien car j’ai collé le code et zou, je suis passé à autre chose.

Le code

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#ifdef _MSC_VER
  #define _CRTDBG_MAP_ALLOC
  #include <crtdbg.h>
#endif
 
#include <iostream>
#include <string>
#include <memory>
 
using namespace std;
 
// ----------------------------------------------------------------------------
class Beverage {
protected:
  string mDescription;
 
public:
  Beverage() : mDescription("Unknown Beverage") {
  }
 
  // Don't forget the "virtual" here
  virtual string getDescription() const {
    return mDescription;
  }
 
  virtual double cost() const = 0;
 
  // See Strategy source code for comments
  virtual ~Beverage() = 0 {}
};
 
// ----------------------------------------------------------------------------
class CondimentDecorator : public Beverage {
public:
  virtual string getDescription() const = 0;
  virtual ~CondimentDecorator() = 0 {}
};
 
// ----------------------------------------------------------------------------
class Espresso : public Beverage {
public :
  Espresso() {
    // TODO : Cannot be done in initialization list since mDescription is in the base.
    mDescription = "Espresso";
  }
   
  double cost() const {
    return 1.99;
  }
};
 
// ----------------------------------------------------------------------------
class HouseBlend : public Beverage {
public:
  HouseBlend() {
    mDescription = "House Blend Coffee";
  }
   
  double cost() const {
    return .89;
  }
};
 
// ----------------------------------------------------------------------------
class Mocha : public CondimentDecorator {
 
private:
  const Beverage *mBeverage;
   
public :
  explicit Mocha(Beverage *beverage) : mBeverage(beverage) {
  }
 
  ~Mocha() {
    delete mBeverage;
  }
   
  string getDescription() const {
    return mBeverage->getDescription() + ", Mocha";
  }
 
  double cost() const {
    return .20 + mBeverage->cost();
  }
};
 
// ----------------------------------------------------------------------------
class Soy : public CondimentDecorator {
 
private:   
  const Beverage *mBeverage;
 
public:
  explicit Soy(Beverage *beverage) : mBeverage(beverage) {
  }
 
  ~Soy() {
    delete mBeverage;
  }
 
  string getDescription() const {
    return mBeverage->getDescription() + ", Soy";
  }
 
  double cost() const {
    return .50 + mBeverage->cost();
  }
};
 
// ----------------------------------------------------------------------------
static void Test(void){
   
  Espresso MyExpresso;
  cout << MyExpresso.getDescription() << " $" << MyExpresso.cost() << endl;
 
  Beverage *beverage = new Espresso;
  cout << beverage->getDescription() << " $" << beverage->cost() << endl;
  delete beverage;
 
  Beverage *OtherBeverage = new HouseBlend;
  OtherBeverage = new Soy(OtherBeverage);
  OtherBeverage = new Mocha(OtherBeverage);
  cout << OtherBeverage->getDescription() << " $" << OtherBeverage->cost() << endl;
  delete OtherBeverage;
}
 
// ----------------------------------------------------------------------------
int main(){
 
#ifdef _MSC_VER
  _CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
#endif
 
  Test(); // Putting all code in Test that way, allow to check memory leaks
 
#ifdef _MSC_VER
  _CrtMemDumpAllObjectsSince(NULL); // Begins the dump from the start of program execution
  _CrtDumpMemoryLeaks();
#endif
 
  cout << endl << "Strike ENTER to exit : ";
  cin.ignore((numeric_limits<streamsize>::max)(), '\n');
}

La suite au prochain épisode…

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