Chapter 14

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Chapter 14

Inheritance

This activity contains 10 questions.

If class C1 inherits from class C2, which of the following is not a term that can be used to describe class C2?

Base classParent classSuper-classDerived class

Given the following class definitions:


// Animal class
class Animal
{
private:
	string type;
	int age;
	string intToString(int i);
public:
	Animal();
	Animal(string newType, int newAge);
	string getDescription();
};

// Cow class
class Cow : public Animal
{
private:
	string breed;
public:
	Cow();
	Cow(int newAge, string newBreed);
	string getBreed();
};

What variables/methods are available for an object of type Cow? e.g. if we declare:


Cow bessie(3,"Holstein");

What can we access after the dot? E.g. can we access bessie.getBreed(), etc?

bessie.getBreed(), bessie.Cow(), bessie.Cow(int newAge, string newBreed), bessie.Animal(), bessie.Animal(string newType, int newAge)bessie.getBreed(), bessie.getDescription()bessie.getBreed()bessie.getBreed(), bessie.Cow(), bessie.Cow(int newAge, string newBreed)

Given the following class definitions:


// Animal class
class Animal
{
private:
	string type;
	int age;
	string intToString(int i);
public:
	Animal();
	Animal(string newType, int newAge);
	string getDescription();
};

// Cow class
class Cow : public Animal
{
private:
	string breed;
public:
	Cow();
	Cow(int newAge, string newBreed);
	void printDescription();
};

What will the following implementation output?


void Cow:: printDescription ()
{
	cout << "Type: " << type << " Breed " <<
		breed << " Age: " << age << endl;
}

Nothing, the program will not compile because the class Cow does not have access to the private variables age and type defined in the base class.The type, breed, and age entered in the constructors.The type and age will be blank variables because they are defined in the base class, but the breed will be output.Nothing, it is not valid to define a method in class Cow that is not declared as virtual in class Animal.

Given the following class definitions:


// Animal class
class Animal
{
protected:
	string type;
	int age;
	string intToString(int i);
public:
	Animal();
	Animal(string newType, int newAge);
	string getDescription();
};

// Cow class
class Cow : public Animal
{
private:
	string breed;
public:
	Cow();
	Cow(int newAge, string newBreed);
	void printDescription();
};

What will the following implementation output?

void Cow:: printDescription ()
{
	cout << "Type: " << type << " Breed " <<
		breed << " Age: " << age << endl;
}

Nothing, the program will not compile because the class Cow does not have access to the protected variables age and type defined in the base class.Nothing, it is not valid to define a method in class Cow that is not declared as virtual in class Animal.The type, breed, and age entered in the constructors.The type and age will be blank variables because they are defined in the base class, but the breed will be output.

Given the following class definitions:


// Animal class
class Animal
{
protected:
	string type;
	int age;
private:
	string intToString(int i);
public:
	Animal();
	Animal(string newType, int newAge);
	string getDescription();
};

// Cow class
class Cow : public Animal
{
private:
	string breed;
public:
	Cow();
	Cow(int newAge, string newBreed);
	void printDescription();
};

What variables and methods are inherited from the Animal class that we can directly access from code written inside the Cow class? (e.g. inside the implementation of printDescription()).

getDescription(), type, agegetDescription(), type, age, intToString()getDescription()getDescription(), intToString()

Given the following definition and implementation of the Cow and Animal classes, what will be the output of the program?


// Animal class
class Animal
{
private:
	string type;
	int age;
	string intToString(int i);
public:
	Animal();
	Animal(string newType, int newAge);
	string getDescription();
};

Animal::Animal()
{
	age=0; type="Unknown";
}

Animal::Animal(string newType, int newAge)
{
	age= newAge; type = newType;
}

// Converts an integer to a string
string Animal::intToString(int i)
{
	stringstream ss;
	ss << i;
	return (ss.str());
}

string Animal::getDescription()
{
	string sAge = intToString(age);
	return string("Animal type: ") + type +
		string(". Age: ") + sAge;
}

// Cow class
class Cow : public Animal
{
private:
	string breed;
public:
	Cow();
	Cow(int newAge, string newBreed);
	string getBreed();
	string getDescription();
};

Cow::Cow() : Animal(), breed("")
{
}

Cow::Cow(int newAge, string newBreed)
  :Animal("cow", newAge), breed(newBreed) 
{
}

string Cow::getBreed()
{
	return breed;
}

string Cow::getDescription()
{
	return Animal::getDescription() + 
		". Breed: " + breed;
}

// Main
int main()
{
	Animal dog("dog",3);
	Cow bessie(4, "holstein");
	cout << dog.getDescription() << endl;
	cout << bessie.getDescription() << endl;
	return 0;
}

Animal type: dog. Age: 3
Animal type: cow. Age: 4

Animal type: dog. Age: 3  Breed:
Animal type: cow. Age: 4  Breed: Holstein

Animal type: dog. Age: 3
Animal type: cow. Age: 4  Breed: Holstein

This program will not compile because C++ does not allow two methods named getDescription() with identical parameter lists.

Given the following class definitions:


// Animal class
class Animal
{
private:
	string type;
	int age;
	string intToString(int i);
public:
	Animal();
	Animal(string newType, int newAge);
	string getDescription();
};

// Cow class
class Cow : public Animal
{
private:
	string breed;
public:
	Cow();
	Cow(int newAge, string newBreed);
	string getDescription();
};

If we define a variable of type Cow, as:  

Cow bessie(3,"Holstein");   

What can we access the getDescription method defined in Animal, not in Cow?

bessie.Animal::getDescription()bessie.getDescription()It is not possible to invoke the getDescription() method defined in Animal from a variable defined of type Cow.Animal::bessie.getDescription()

Out of constructors, destructors, and the overloaded assignment operator, which are inherited in a derived class?

Constructors, DestructorsNone of these.All of these.Assignment

Given the following class definitions:


// Animal class
class Animal
{
private:
	string type;
	int age;
	string intToString(int i);
public:
	Animal();
	Animal(string newType, int newAge);
	virtual string getDescription();
};

Animal::Animal()
{
	age=0; type="Unknown";
}

Animal::Animal(string newType, int newAge)
{
	age= newAge; type = newType;
}

// Converts an integer to a string
string Animal::intToString(int i)
{
	stringstream ss;
	ss << i;
	return (ss.str());
}

/*
string Animal::getDescription()
{
	string sAge = intToString(age);
	return string("Animal type: ") + type +
		string(". Age: ") + sAge;
}
*/

// Cow class
class Cow : public Animal
{
private:
	string breed;
public:
	Cow();
	Cow(int newAge, string newBreed);
	string getBreed();
	string getDescription();
};

Cow::Cow() : Animal(), breed("")
{
}

Cow::Cow(int newAge, string newBreed)
  :Animal("cow", newAge), breed(newBreed) 
{
}

string Cow::getBreed()
{
	return breed;
}

string Cow::getDescription()
{
	return Animal::getDescription() + 
		". Breed: " + breed;
}

What will the following code output?


	Animal a;
	Cow bessie(4, "holstein");
	a = bessie;
	cout << a.getDescription() << endl;

Animal type: cow. Age: 4Nothing, the code will not compile because we cannot assign variable bessie to variable a. Variable bessie is of type Cow, while variable a is of type Animal.Animal type: cow. Age: 4. Breed: holsteinNothing, the program will not compile because C++ does not allow two methods named getDescription() with identical parameter lists.

Given the following class definitions:


// Animal class
class Animal
{
private:
	string type;
	int age;
	string intToString(int i);
public:
	Animal();
	Animal(string newType, int newAge);
	virtual string getDescription();
};

Animal::Animal()
{
	age=0; type="Unknown";
}

Animal::Animal(string newType, int newAge)
{
	age= newAge; type = newType;
}

// Converts an integer to a string
string Animal::intToString(int i)
{
	stringstream ss;
	ss << i;
	return (ss.str());
}

/*
string Animal::getDescription()
{
	string sAge = intToString(age);
	return string("Animal type: ") + type +
		string(". Age: ") + sAge;
}
*/

// Cow class
class Cow : public Animal
{
private:
	string breed;
public:
	Cow();
	Cow(int newAge, string newBreed);
	string getBreed();
	string getDescription();
};

Cow::Cow() : Animal(), breed("")
{
}

Cow::Cow(int newAge, string newBreed)
  :Animal("cow", newAge), breed(newBreed) 
{
}

string Cow::getBreed()
{
	return breed;
}

string Cow::getDescription()
{
	return Animal::getDescription() + 
		". Breed: " + breed;
}

What will the following code output?


	Animal mr_ed("cow",4);
	Cow cow5;
	cow5 = mr_ed;
	cout << cow5.getDescription() << endl;

Nothing, the program will not compile because C++ does not allow two methods named getDescription() with identical parameter lists.Animal type: cow. Age: 4Animal type: cow. Age: 4. Breed:Nothing, the code will not compile because we cannot assign variable mr_ed to variable cow5. Variable cow5 is of type Cow, while variable mr_ed is of type Animal.

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