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LW: Class Constructors Objectives Write a default constructor for a class. Note that this const...

LW: Class Constructors

Objectives

  • Write a default constructor for a class. Note that this constructor is used to build the object anytime an argument is not provided when it is defined.

  • Write a parameterized constructor that takes arguments that are used to initialize the class’s member variables

Labwork

  1. Download the code associated with this lab:

    • ColorConstructor.zip

      1. Main.cpp

      2. Color.h

      3. Color.cpp

  2. Compile and run the code.

    • The first line of output of the program should display nonsensical integers for the values of the color object declared on line 5, for example:
      Color values after declaration : (1355559696,32767,1764024374)

    • The program will then prompt you to input the r, g, and b values of a color, which will be assigned to the corresponding members of the color object, provided that they are valid (within the range 0-255).

  3. Create a default constructor that initializes the r, g, and b members to 255. After you've done this, compile your code and run the program. The output should be similar to that presented below:
    Color values after declaration: (255,255,255)
    followed by the previously observed input prompt.

  4. Create a parameterized constructor (this will be a new, additional constructor; leave the constructor that you modified in the previous step as is) that:

    • takes integer arguments for r, g, and b;

    • initializes the Color object’s members R, G, and B to the passed parameters r, g, and b using the initializer list syntax;

    • in the body, checks whether R, G, and B are valid values; if not, you should throw an instance of Color_error{} (throw Color_error{}).

  5. Let's test the code that you've written in the previous step. Comment out the code falling between //Part 1 and //Part 2; Uncomment the code below Part 2.

  6. Compile and run your code.

  7. Test your constructor by providing valid and invalid R,G,B values as input.

Main.cpp

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
// CLASS CONSTRUCTORS LAB //
// MAIN.CPP //
// //
// Date ...: 18/MAR/2017 //
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

//////////////////////////////////////////////////////////////////////////////
// Includes //
//////////////////////////////////////////////////////////////////////////////
#include <iostream>
#include <string>
#include <limits>
#include "Color.h"
using namespace std;

//////////////////////////////////////////////////////////////////////////////
// main //
//////////////////////////////////////////////////////////////////////////////

int main(int argc, char *argv[])
{
string prompt = "Please enter the r, g, and b integer values of a color, \nwith each separated by a space (e.x., \"255 255 255\"): ";
// Part 1
Color color;
cout << "Color values after declaration : " << color.to_str() << endl;
char cont = 'y'; // continue is yes
while (tolower(cont) == 'y') {
cout << prompt;
   int r, g, b;
while (!(cin >> r >> g >> b)) {
if (cin.bad() || cin.eof()) {
return 1;
} else if (cin.fail()) {
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
cout << "Invalid input." << endl << endl << prompt;
}
try {
           color.set_R(r); color.set_G(g); color.set_B(b);
           cout << "Color : " << color.to_str() << endl << endl;
}
catch (Color_error& e) {
   cout << "Invalid input." << endl << endl;
}
cout << "Do another? (y or Y) ";
cin >> cont;
}
/*
// Part 2
char cont = 'y'; // continue is yes
while (tolower(cont) == 'y') {
cout << prompt;
   int r, g, b;
while (!(cin >> r >> g >> b)) {
if (cin.bad() || cin.eof()) {
return 1;
} else if (cin.fail()) {
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
cout << "Invalid input." << endl << endl << prompt;
}
try {
           Color color(r, g, b);
           cout << "Color : " << color.to_str() << endl << endl;
}
catch (Color_error& e) {
   cout << "Invalid input." << endl << endl;
}
cout << "Do another? (y or Y) ";
cin >> cont;
}
*/
cout << "Goodbye!" << endl;
return 0;
}
Color.h

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
// CLASS CONSTRUCTORS LAB //
// COLOR.H //
// //
// Date ...: 18/MAR/2017 //
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
#ifndef COLOR_H
#define COLOR_H

//////////////////////////////////////////////////////////////////////////////
// Dependencies //
//////////////////////////////////////////////////////////////////////////////
#include <iostream>
#include <string>
#include <sstream>

//////////////////////////////////////////////////////////////////////////////
// Color Class Definition //
//////////////////////////////////////////////////////////////////////////////
class Color_error {};
class Color {
public:
std::string to_str();
bool is_valid_val(int);
void set_R(int);
void set_G(int);
void set_B(int);
private:
int R;
int G;
int B;
};
//////////////////////////////////////////////////////////////////////////////
#endif

Color.cpp

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
// CLASS CONSTRUCTORS LAB //
// COLOR.CPP //
// //
// Date ...: 18/MAR/2017 //
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

//////////////////////////////////////////////////////////////////////////////
// Includes //
//////////////////////////////////////////////////////////////////////////////
#include "Color.h"

//////////////////////////////////////////////////////////////////////////////
// Color Class Member Definitions //
//////////////////////////////////////////////////////////////////////////////
std::string Color::to_str()
{
std::stringstream ss;
ss << '(' << R << ',' << G << ',' << B << ')';
return ss.str();
}

void Color::set_R(int r)
{
if (!is_valid_val(r))
throw Color_error{};
R = r;
}
void Color::set_G(int g)
{
if (!is_valid_val(g))
throw Color_error{};
G = g;
}
void Color::set_B(int b)
{
if (!is_valid_val(b))
throw Color_error{};
B = b;
}
bool Color::is_valid_val(int v)
{
if (v < 0 || v > 255)
return false;
else
return true;
}

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Homework Answers

Answer #1

Done. Updated the classes: Color.h and Color.cpp to add two constructors

Main.cp: Updated to test the functionality. Commented part 1 and uncommented part 2

////////////////////////////////////////////////Color.h/////////////////////////////////////////////////////////////

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
// CLASS CONSTRUCTORS LAB //
// COLOR.H //
// //
// Date ...: 18/MAR/2017 //
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
#ifndef COLOR_H
#define COLOR_H

//////////////////////////////////////////////////////////////////////////////
// Dependencies //
//////////////////////////////////////////////////////////////////////////////
#include <iostream>
#include <string>
#include <sstream>

//////////////////////////////////////////////////////////////////////////////
// Color Class Definition //
//////////////////////////////////////////////////////////////////////////////
class Color_error {};
class Color {
public:
Color();
Color(int,int,int);
std::string to_str();
bool is_valid_val(int);
void set_R(int);
void set_G(int);
void set_B(int);
private:
int R;
int G;
int B;
};

#endif

/////////////////////////////////////////////////End Color.h/////////////////////////////////////////////////////////////////////////////////////

/////////////////////////////////////////////////////Color.cpp//////////////////////////////////////////////////////////////////////////////////


#include "Color.h"

//////////////////////////////////////////////////////////////////////////////
// Color Class Member Definitions //
//////////////////////////////////////////////////////////////////////////////

//Default constructor that initialises R,G,B to 255
Color::Color() {
R = 255;
G = 255;
B = 255;
}
//Parameterise constructor that initialises R,G,B to values passed by the user. if there is
// some invalid value color exception is thrown
Color::Color(int r, int g, int b) {
if (!is_valid_val(g) || !is_valid_val(r) || !is_valid_val(b))
throw Color_error {
};

R = r;
G = g;
B = b;
}

std::string Color::to_str() {
std::stringstream ss;
ss << '(' << R << ',' << G << ',' << B << ')';
return ss.str();
}

void Color::set_R(int r) {
if (!is_valid_val(r))
throw Color_error {
};
R = r;
}

void Color::set_G(int g) {
if (!is_valid_val(g))
throw Color_error {
};
G = g;
}

void Color::set_B(int b) {
if (!is_valid_val(b))
throw Color_error {
};
B = b;
}

bool Color::is_valid_val(int v) {
if (v < 0 || v > 255)
return false;
else
return true;
}
/////////////////////////////////////////////////////End Color.cpp///////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////main.cpp///////////////////////////////////////////////////////////////////////

#include <iostream>
#include <string>
#include <limits>
#include "Color.h"
using namespace std;

//////////////////////////////////////////////////////////////////////////////
// main //
//////////////////////////////////////////////////////////////////////////////

int main(int argc, char *argv[]) {
string prompt = "Please enter the r, g, and b integer values of a color, \nwith each separated by a space (e.x., \"255 255 255\"): ";
/*
// Part 1
Color color ;
cout << "Color values after declaration : " << color.to_str() << endl;
char cont = 'y'; // continue is yes
while (tolower(cont) == 'y') {
cout << prompt;
int r, g, b;
while (!(cin >> r >> g >> b)) {
if (cin.bad() || cin.eof()) {
return 1;
} else if (cin.fail()) {
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
cout << "Invalid input." << endl << endl << prompt;
}
try {
color.set_R(r);
color.set_G(g);
color.set_B(b);
cout << "Color : " << color.to_str() << endl << endl;
} catch (Color_error& e) {
cout << "Invalid input." << endl << endl;
}
cout << "Do another? (y or Y) ";
cin >> cont;
}
*/
// Part 2
char cont = 'y'; // continue is yes
while (tolower(cont) == 'y') {
cout << prompt;
int r, g, b;
while (!(cin >> r >> g >> b)) {
if (cin.bad() || cin.eof()) {
return 1;
} else if (cin.fail()) {
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
cout << "Invalid input." << endl << endl << prompt;
}
try {
Color color(r, g, b);
cout << "Color : " << color.to_str() << endl << endl;
}
catch (Color_error& e) {
cout << "Invalid input." << endl << endl;
}
cout << "Do another? (y or Y) ";
cin >> cont;
}

cout << "Goodbye!" << endl;
return 0;
}

/////////////////////////////////////////////////////////End main.cpp////////////////////////////////////////////////////////

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