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Please Please Help me - reading class member data into an array using a class member function

anthony1947 (10)
Hello,

The programme I have developed so far does the following:
1. Writes to a file (route1.txt) the details of a planet - planet id, x, y and z coordinates using the function get_details()
2. Reads from the file using the fuinction generate_planet()
3. Outputs the data from the file onto the screen using report_planet()

In the function report_planet(), I want to read the the class data (planet id, x, y, and z coordinates) reported by report_planet() into an array. Once I have this array, I want to feed this array of planet data into my function total_route_length(). Can you advise me on how to do this successfully?

Here is the programme:

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#include <iostream>
#include <fstream>
#include <cmath>

using namespace std;

class planet
{
private:
	float planet_id, x, y, z;

public:
	planet ();
	planet (float, float, float, float);
	planet (const planet &copy_planet);
	~planet();
	void get_details(ofstream &fout);
	void generate_planet (ifstream &fin);
	planet report_planet ();
	float total_route_length (planet *first_planet, planet *second_planet);
};

planet::planet ()
{
	planet_id = 0.0;
	x = 0.0;
	y = 0.0;
	z = 0.0;
}

planet::planet (float id, float x_coord, float y_coord, float z_coord)
{
	planet_id = id;
	x = x_coord;
	y = y_coord;
	z = z_coord;
}

planet::planet (const planet &copy_planet)
{
	planet_id = copy_planet.planet_id;
	x = copy_planet.x;
	y = copy_planet.y;
	z = copy_planet.z;
}

planet::~planet()
{
	planet_id = 0.0;
	x = 0.0;
	y = 0.0;
	z = 0.0;
}

void planet::get_details (ofstream &fout)
{
	cout << "Enter the details for Planet " << endl;
	cout << "Enter the Planet's ID: ";
	cin >> planet_id;
	fout << planet_id << "\t";
	cout << "Enter the planet's x coordinate: ";
	cin >> x;
	fout << x << "\t";
	cout << "Enter the planet's y coordinate: ";
	cin >> y;
	fout << y << "\t";
	cout << "Enter the planet's z coordinate: ";
	cin >> z;
	fout << z << endl;
	cout << endl;
}

void planet::generate_planet (ifstream &fin)
{ 
	fin >> planet_id;
	fin >> x;
	fin >> y;
	fin >> z;
}

planet planet::report_planet ()
{
	planet *new_planet = new planet;
	cout << "Planet's ID: " << planet_id << endl;
	cout << "x coordinate: " << x << endl;
	cout << "y coordinate: " << y << endl;
	cout << "z coordinate: " << z << endl;
	cout << "\n";
	return *new_planet;
}

float planet::total_route_length (planet *first_planet, planet *second_planet)
{
	if ((first_planet -> planet_id)==1)
	{
		float base_distance = sqrt(pow((first_planet -> x) - 0,2) + pow((first_planet -> y) - 0,2) + pow((first_planet -> z) - 0,2));
		float result = base_distance + sqrt(pow((first_planet -> x) - (second_planet -> x),2) + pow((first_planet -> y) - (second_planet -> y),2) + pow((first_planet -> z) - (second_planet -> z),2));
		return result;
	}
	if ((second_planet -> planet_id)==1)
	{
		float base_distance = sqrt(pow(0 - (second_planet -> x),2) + pow(0 - (second_planet -> y),2) + pow(0 - (second_planet -> z),2));
		float result = base_distance + sqrt(pow((first_planet -> x) - (second_planet -> x),2) + pow((first_planet -> y) - (second_planet -> y),2) + pow((first_planet -> z) - (second_planet -> z),2));
		return result;
	}
	if ((first_planet -> planet_id)>1 && (second_planet -> planet_id)>1)
	{
		float result = sqrt(pow((first_planet -> x) - (second_planet -> x),2) + pow((first_planet -> y) - (second_planet -> y),2) + pow((first_planet -> z) - (second_planet -> z),2));
		return result;
	}
}

void main()
{
	int i, temp_size;
	float distance = 0;
	planet mars;
	planet the_red_one(mars);
	
	ofstream fout;
	fout.open ("route1.txt");
	cout << "Enter the number of planets: ";
	cin >> temp_size;
	fout << temp_size << endl;
	cout << endl;
	for (i=0; i<temp_size; i++)
		mars.get_details (fout);
	fout.close ();

	ifstream fin;
	fin.open ("route1.txt");
	fin >> temp_size;
	planet *the_planets = new planet [temp_size];
	for (i=0; i<temp_size; i++)
	{
		//int j=j+1;
		mars.generate_planet (fin);
		the_planets[i] = mars.report_planet ();
		//if (j>(temp_size-1)) 
			//j = 0;
		//distance = distance + mars.total_route_length (the_planets[i], the_planets[j]);		//pass pointer to planet to calculate distance between planets
		//if (j==0)
			//cout << "The Total Route Length is: " << distance << endl;
	}
	fin.close ();

	cin.sync ();
	cin.get ();
}
Last edited on
Thazager (10)
for the total_route_length() function:
calculate the distance from x,y,z [location] to next x,y,z [location], and add them together.
planetDist[0] + planetDist[1] ... in a loop.

for read data into array:
Here are 2 functions from Nehe, that load text files. They are in lesson 10 on his site at http://nehe.gamedev.net/default.asp The rest of the values are there for these 2 functions, along with the text file that they read from.
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void readstr(FILE *f,char *string)
{
	do
	{
		fgets(string, 255, f);
	} while ((string[0] == '/') || (string[0] == '\n'));
	return;
}

void SetupWorld()
{
	float x, y, z, u, v;
	int numtriangles;
	FILE *filein;
	char oneline[255];
	filein = fopen("data/world.txt", "rt");				// File To Load World Data From

	readstr(filein,oneline);
	sscanf_s(oneline, "NUMPOLLIES %d\n", &numtriangles);

	sector1.triangle = new TRIANGLE[numtriangles];
	sector1.numtriangles = numtriangles;
	for (int loop = 0; loop < numtriangles; loop++)
	{
		for (int vert = 0; vert < 3; vert++)
		{
			readstr(filein,oneline);
			sscanf_s(oneline, "%f %f %f %f %f", &x, &y, &z, &u, &v);
			sector1.triangle[loop].vertex[vert].x = x;
			sector1.triangle[loop].vertex[vert].y = y;
			sector1.triangle[loop].vertex[vert].z = z;
			sector1.triangle[loop].vertex[vert].u = u;
			sector1.triangle[loop].vertex[vert].v = v;
		}
	}
	fclose(filein);
	return;
}

anthony1947 (10)
Thanks for your response Thazager! With your information, I have further increased my C++ repertoire.

In relation to this post, the question I would really like answered is: How do I implement a function that takes no argument but returns an array that contains new values for class objects?

In my particular code, I would like to achieve this with the report_planet() function; it takes no arguments but it should return an array that houses new values for planet_id, x, y and z. I would also like to keep the generate_planet() function as the only class member function that reads data from a file.

Is this possible? If it is, I would be grateful if someone could provide the code or even a helpful hint. Please help me!
Last edited on
anthony1947 (10)
I really need some advice... please please help!
LB (13399)
Why can't you have it return an actual planet object?
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