Homework #2 Solution




  • Object-oriented programming

    • Data Hiding

    • Encapsulation

    • Delegation


We will expand our Warrior a little. Each Warrior will have a weapon. He is “born” with it, i.e. the weapon is created together with the warrior. It can only be accessed by him. It provides him with his strength. In battle, weapons lose their edge and weaken. When a Warrior’s weapon loses all of its strength, the Warrior himself dies.


  • What are the types of things in the problem? We will need a class for each type.

  • What do the things / types do? These “behaviors” should be represented as methods.

  • Weapons have both a name and a strength. The weapon is created together with the Warrior and cannot be accessed by anyone else.

  • The input file needs to change a little. When a Warrior is created, instead of simply specifying his name and strength, the command will specify the Warrior’s name as well as his Weapon’s name and its strength.

  • The Status report will also be modified to show the name of the Warrior’s Weapon.

  • No one can access a warrior’s weapon accept the warrior himself. But the weapon is what actually holds the warrior’s strength. How does this effect the programming? Any time the code needs to know or change the warrior’s strength, the warrior then asks the weapon what the strength is or tells the weapon that the strength needs to be changed. This represents the idea of delegation. We will see this concept frequently, where one object requests that another object do some task.


Our sample input file might now look like:

Warrior Jim Glamdring 42
Warrior Lancelot Naegling 15
Warrior Arthur Excalibur 15
Warrior Torvalds Narsil 20
Warrior Gates Orcrist 8
Battle Arthur Lancelot
Battle Jim Lancelot
Battle Torvalds Gates
Battle Gates Lancelot


The corresponding output would be:

There are: 5 warriors
Warrior: Jim, weapon: Glamdring, 42
Warrior: Lancelot, weapon: Naegling, 15
Warrior: Arthur, weapon: Excalibur, 15
Warrior: Torvalds, weapon: Narsil, 20
Warrior: Gates, weapon: Orcrist, 8
Arthur battles Lancelot
Mutual Annihilation: Arthur and Lancelot die at each other’s hands
Jim battles Lancelot
He’s dead, Jim
Torvalds battles Gates
Torvalds defeats Gates
Gates battles Lancelot
Oh, NO! They’re both dead! Yuck!
There are: 5 warriors
Warrior: Jim, weapon: Glamdring, 42
Warrior: Lancelot, weapon: Naegling, 0
Warrior: Arthur, weapon: Excalibur, 0
Warrior: Torvalds, weapon: Narsil, 12
Warrior: Gates, weapon: Orcrist, 0

Turn in

Hand in a single cpp file, hw02.cpp, containing your program.

Grading Comments:

In main(), item object should not be instantiated here. The warrior constructor should accept 3 parameters warriorName, weaponName and strength. The constructor should instantiate a Weapon item in the member initialization list.

Weapon item(weaponName, str);
Warrior awarrior(name, item);

In method battleWith of class Warrior, to get or set a warrior’s strength, call a method in the Warrior to get or set the strength which in turn calls the respective method in the Weapon class.

Use functions to process the file, handle each command like “Battle”, “Warrior” and “Status”.

void display() in  class Warrior and int getStr() in Weapon should be a const method.