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lab_inheritance

Insidious Inheritance

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Assignment Description

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D#6;=26=65%;98;%=69#B=;86C#%=>%8%C98B8C;#B=>;=C%2E%8??%2'I#C;%2B=#6;#:%AB25B8DD=65%?865"85#>F%J"B%528?%=>%;2

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E";"B#F%0?#8>#%B#8:%;9B2"59%;9#%#6;=B#%?8'%'#E2B#%42"%'#5=6F

Lab Insight

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O2D#%C?8>>#>%;98;%E"B;9#B%#3;#6:%26%;9#>#%C26C#A;>%=6C?":#%GO%P+Q*%GO%+P+*%86:%GO%P++F%M9=>%?8'%@=??%9#?A

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Getting Set Up

&B2D%42"B%GO%++.%5=;%:=B#C;2B4*%B"6%;9#%E2??2@=65%26%VWO$

git fetch release

git merge release/lab_inheritance -m "Merging initial lab_inheritance files"

<E%42"YB#%26%42"B%2@6%D8C9=6#*%42"%D84%6##:%;2%B"6$

git fetch release

git merge --allow-unrelated-histories release/lab_inheritance -m "Merging initial

lab_inheritance files"

Assignment

Description

Lab Insight

Getting Set Up

Class

Hierarchy

Exercise 1: Fix

the Virtual

Methods

Exercise 2: Fix

the Destructor

Exercise 3: Fix

the

Constructor

Exercise 4: Fix

the Pure

Virtual Method

Exercise 5: Fix

the Slicing

Testing Your

Code

Cleaning up

files

Submitting

Your Work

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M9#%C2:#%E2B%;9=>%8C;=K=;4%B#>=:#>%=6%;9#%lab_inheritance/%:=B#C;2B4F%\#;%;9#B#%'4%;4A=65%;9=>%=6%42"B%@2BL=65

:=B#C;2B4$

cd lab_inheritance/

Class Hierarchy

M2%9#?A%">%"6:#B>;86:%C?8>>%9=#B8BC9=#>%'#;;#B%9#B#%=>%86%#38DA?#%2E%8%>=DA?#%C?8>>%9=#B8BC94%>92@=65%;98;%8

Dog%is a%AnimalF

M9#%C2:#%@2"?:%?22L%>2D#;9=65%?=L#%;9#%E2??2@=65$

class Animal {

public:

string name;

virtual void speak() = 0;

/* The = 0 at the end of the method means that the method is a pure virtual method

* meaning that it does not have an implementation and it delegates the task

* of implementing the method to the classes that is derived from it */

};

class Dog : public Animal {

public:

string breed;

/* Dog inherits speak from Animal */

void speak();

};

void Dog::speak() {

cout << "Woof Woof" << endl;

}

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;9#B#E2B#*%=;%=69#B=;>%8%name%86:%8%speak%D#;92:%EB2D%AnimalF%^2@#K#B*%>=6C#%;9#%AnimalY>%speak%:2#>%62;

98K#%86%=DA?#D#6;8;=26*%Dog%must%=DA?#D#6;%;9#%speak%D#;92:F

!%_2"%@=??%26?4%6##:%;2%D2:=E4%;9#%E2??2@=65%E=?#>$

shape.{cpp,h}

circle.{cpp,h}

truck.{cpp,h}

flower.{cpp,h}

drawable.h

^#B#%=>%86%#38DA?#%2E%92@%@#%C2"?:%">#%8%Dog%2'I#C;$

Dog* d = new Dog();

/* Like usual we can access all the public methods and member variables of a

* Dog */

d->breed;

/* But now since a Dog is an Animal we can also do this too */

d->name; // inherited from Animal

d->speak(); // inherited from Animal and since it is a Dog speak() will print

// "Woof Woof"

/* Additionally we can treat our Dog only like an Animal like this */

Animal* a = d;

/* But now we can only do the following */

a->name;

a->speak(); // Still prints "Woof Woof" because speak is a virtual method.

a->breed // ERROR! This will NOT work since we perceive it as an Animal now

/* Additionally, if we try to have our Animal pointer point back to a Dog

* pointer this will cause a problem because an Animal Is NOT A Dog. */

Dog* d2 = a; // ERROR! Animal Is NOT A Dog

/* Furthermore, since Animal is abstract and has a pure virtual method

* we CANNOT construct one! */

Animal a2; // ERROR! Animal is an abstract class

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8CC#A;8'?#$

Drawable* triangle = new Triangle(....);

Drawable* circle = new Circle(...);

Drawable* rectangle = new Rectangle(....);

Drawable* truck = new Truck(...);

Drawable* flower = new Flower(....);

/* Now the only thing we can use on triangle, circle, rectangle, truck, and

* flower is draw but what gets drawn will change depending on what type the

* pointer is actually pointing to. This is called polymorphism, the behavior

* changes depending on the actual type of the object being pointed to. */

PNG canvas;

triangle->draw(&canvas); // draws a Triangle even though triangle is a Drawable*

circle->draw(&canvas); // draws a Circle even though circle is a Drawable*

rectangle->draw(&canvas); // draws a Rectangle even though rectangle is a Drawable*

truck->draw(&canvas); // draws a Truck even though truck is a Drawable*

flower->draw(&canvas); // draws a Flower even though flower is a Drawable*

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lab_inheritanceF

&2B%#38DA?#%@9#6%42"%B"6

./lab_inheritance

_2"%C2"?:%8?>2%B"6%Valgrind%26%;9#%62BD8?%#3#C";8'?#$

valgrind --leak-check=full ./lab_inheritance

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Exercise 1: Fix the Virtual Methods

0?#8>#%'"=?:%86:%B"6%test_virtual$

make test_virtual # compile to produce test_virtual executeble

valgrind ./test_virtual # run test_virtual with valgrind

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The Perimeters are NOT the same.

The Areas are NOT the same.

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test_virtual.cpp%A2=6;%;2%;9#%>8D#%2'I#C;b

Exercise 2: Fix the Destructor

0?#8>#%'"=?:%86:%B"6%test_destructor$

!%Exercise

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M2%E=3%;9=>%AB2'?#D%42"%>92"?:%26?4%6##:%;2%D2:=E4%shape.cpp%86:c2B%shape.hF

make test_destructor # compile to produce test_destructor

executeble

valgrind --leak-check=full ./test_destructor # run test_destructor in valgrind

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42"%?22L%C?2>#?4*%Triangle%:2#>%98K#%8%K8?=:%:#>;B"C;2B%86:%=;%=>%'#=65%C8??#:%=6%test_destructorb

Exercise 3: Fix the Constructor

0?#8>#%'"=?:%86:%B"6%test_constructor$

make test_constructor # make test_constructor

./test_constructor # run test_constructor

W9#6%42"%B"6%test_constructor%42"%@=??%>##%;9#%E2??2@=65%2";A";$

Circle's color is NOT correct!

Circle's center is NOT correct!

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86:%@9#6%@#%8>L%E2B%;9#%CircleY>%C#6;#B%86:%C2?2B%;9#4%8B#%62;%;9#%>8D#b

Exercise 4: Fix the Pure Virtual Method

0?#8>#%'"=?:%86:%B"6%test_pure_virtualF

!%Exercise

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M2%E=3%;9=>%AB2'?#D%42"%>92"?:%26?4%6##:%;2%D2:=E4%drawable.h%86:%shape.hF

!%Exercise

<6K#>;=58;#%86:%E=3%;9#%C2:#%>2%;98;%;9#%Circle%=>%'#=65%C26>;B"C;#:%@=;9%;9#%AB2A#B%C#6;#B%86:

C2?2BF

M2%E=3%;9=>%AB2'?#D%42"%>92"?:%26?4%6##:%;2%D2:=E4%circle.cpp

M9#%C2BB#C;%test_constructor.png%>92"?:%?22L%?=L#%;9#%E2??2@=65$

make test_pure_virtual # make test_pure_virtual

./test_pure_virtual # run test_pure_virtual

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^2@#K#B*%=E%42"%?22L%8;%;9#%truck.{h,cpp}%=;%=>%8%E"??4%E#8;"B#:%C?8>>b%W94%=>%=;%62;%C2DA=?=65d

Exercise 5: Fix the Slicing

0?#8>#%'"=?:%86:%B"6%test_slicing%@=;9$

make test_slicing # make test_slicing

./test_slicing # run test_slicing

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:B8@6F%&2B%>2D#%B#8>26%I">;%8%'"6C9%2E%eY>%98>%'##6%:B8@6%86:%8%B#:%C=BC?#F

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@#%;B4%;2%:B8@%;9#D%;9#4%8B#%:B8@6%=6C2BB#C;?4F

Testing Your Code

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!%Exercise

<6K#>;=58;#%86:%E=3%;9#%C2:#%>2%;98;%test_pure_virtual%C2DA=?#>*%B"6>*%86:%2";A";>%8%TruckF

M2%E=3%;9=>%AB2'?#D%42"%>92"?:%26?4%6##:%;2%D2:=E4%truck.h%86:%truck.cppF

<6%2B:#B%;2%98K#%;9#%Truck%:B8@%AB2A#B?4%42"%@=??%E=B>;%6##:%;2%98K#%V3#BC=>#%,%C2DA?#;#:F

M9#%C2BB#C;%test_pure_virtual.png%>92"?:%?22L%?=L#%;9#%E2??2@=65$

!%Exercise

<6K#>;=58;#%86:%E=3%;9#%C2:#%>2%;98;%test_slicing%2";A";>%8%FlowerF

M2%E=3%;9=>%AB2'?#D%42"%>92"?:%26?4%6##:%;2%D2:=E4%flower.h%86:%flower.cppF

_2"%D">;%">#%A2?4D2BA9=>Db

M9#%C2BB#C;%test_slicing.png%2";A";%>92"?:%?22L%?=L#%;9#%E2??2@=65$

make test

./test

Cleaning up files

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E2??2@=65%C2DD86:$

make clean

Submitting Your Work

M9#%E2??2@=65%E=?#>%8B#%">#:%;2%5B8:#%;9=>%8>>=56D#6;$

shape.cpp

shape.h

circle.cpp

circle.h

truck.cpp

truck.h

flower.cpp

flower.h

drawable.h

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"%\"=:#$%^2@%;2%>"'D=;%GO%++.%@2BL%">=65%5=;

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