CSE2305 - Object-Oriented Software Engineering
exercises

CSE2305
Object-Oriented Software Engineering

Exercise 3: Animal Hospital: solution

You were asked to create a simple database to help the animal hospital using inheritance.

Observations:

The class hierarchy is already in the question so this tutorial is in basic terms translating UML into C++. First the base class, Animal. Here a couple of utility methods have been added (not in the UML diagram). Two methods are pure virtual meaning that we can't instantiate an instance of Animal - more detail is required in a derived class.

Animal.h

class Animal {
 public:
    enum SexType { Indeterminate, Male, Female, Hermaphrodite };
    typedef unsigned int Days;


    Animal(const string& name,
                 int ageInYears,
                 SexType sex,
                 const Date& arrived = Date::Today(), const Date& departure = Date::Today());
    virtual ~Animal(void);
    
    void arrived(const Date& arrivalDate = Date::Today());
    void departed(const Date& departureDate = Date::Today());
    void setName(const string& name);
    void setAgeInYears(int y);
    void setSexType(SexType s);


    Days getLengthOfStay(void) const;
    const string& getName() const;
    int getAgeInYears() const;
    SexType getSexType() const;


    virtual const string& getTypeName() const { return "Animal"; }
    virtual int numberOfLegs(void) = 0; // pure virtual
    virtual int feedsPerDay(void) = 0;
    virtual void printDetails(ostream& s)  {
      s << getName() << " (" << getTypeName() << ")  with " << numberOfLegs() << " legs. Arrived " <<
      getArrivalDate() << ", staying " << getLengthOfStay() << " days." << endl;
      s << "Requires " << feedsPerDay() << " feeds per day." << endl;
    }
 protected:
    Date myArrivalDate;
    Date myDepartureDate;
    string myName;
   int myAgeInYears;
   SexType mySex;
};

Next, the Cat class:

Cat.h

class Cat : public Animal {
 public:
        Cat(const string& name,
                 int ageInYears,
                 SexType sex,
                 const Date& arrived = Date::Today(), const Date& departure = Date::Today());
    
    virtual const string& getTypeName() const { return "Cat"; }
    virtual int numberOfLegs(void) { return numberOfLegs - legsMissing; }
    virtual int feedsPerDay(void)  { return feedsPerDay; }
    
    void setFeedsPerDay(int numberOfFeeds);
    void setNumberOfLegsMissing(int n);

 private:
     int legsMissing;
     int feedsPerDay;
     const int numberOfLegs = 4;
};

Let's look at the Cat constructor:

Cat.cpp

 
      #include "Cat.h"
Cat::Cat(const string& name, int ageInYears, 
                SexType sex, const Date& arrived, 
                const Date& departed) :
    Animal(name, ageInYears, sex, arrived, departed),
    legsMissing(0),
    feedsPerDay(2)
{
}
    .
    .
    .

The other derived classes should be easy. Some questions to consider:

• Why is feedsPerDay() not const? Should it be?

• How much code is in common between Cat and Dog? (refer tute questions).

The question also called for a simple database class (AnimalHospital). Here we could use the List class (from Assignment 1) to implement the AnimalHospital class. Something to think about – should AnimalHospital inherit from List, or should List be a private data member of AnimalHospital?

Last modified: September 5, 2005

CSE2305 Object-Oriented Software Engineering

Exercise 3: Animal Hospital: solution

CSE2305
Object-Oriented Software Engineering