Creating Shapes: Exploring Area & Descriptions

[ghost305]

#ifndef SHAPE_H
#define SHAPE_H

#include <string.h>
using std::string;

using namespace std;



class Shape

{
public:
	Shape(const string &color); //constructor
	~Shape();
	string getColor()const; //returns objects color value
	virtual double area()const = 0;// a const pure virtual member function that computes and returns the object's area
	virtual string toString() const = 0; //a const pure virtual member function that returns the shape's description
private:
	string s_color;

};


#endif //SHAPE_H

#include <string>
using std::string;

#include <sstream>

#include <iostream>
using std::cout;
using std::cin;
using std::endl;

#include "square.h"

//ctor
square::square(const string &color, double length)
:Shape(color)
{
	length = len;
}//end ctor

//dtor
double square::getLength()
{
	return len;
}
//Function to calculate are
double square::area()const
{
	return len * len;
}//end function to calculate area

//Function to returns square's description
string square::toString()const
{
  ostringstream os;
  os << getColor() <<"square with side length of " << len << " " << "and area of " << area();
  return os.str();

}//end of function to return's square description

#include <string>
using std::string;

#include <sstream>

#include <iostream>
using std::cout;
using std::cin;
using std::endl;

#include "rectangle.h"

//ctor
rectangle::rectangle(const string &color, double width, double length)
:Shape(color)
{
length = len;
wid = width;
}//end ctor

//dtor
double rectangle::getWidth()
{
	return wid;
}

double rectangle::getLength()
{
	return len;
}
//function to calculate rectangle area
double rectangle::area() const
{
	return len * wid;
}//end function to get rectangle area

//returns rectangle's description
string rectangle::toString()const
{
  ostringstream os;
  os << getColor() <<"rectangle with length of " << len << " and width of " << wid << " and area of " << area();
  return os.str();
}//end function to return rectangle's description


#include <string>
using std::string;

#include <sstream>

#include <iostream>
using std::cout;
using std::cin;
using std::endl;

#include "circle.h"

//ctor
circle::circle(const string& color, double radius)
:Shape(color)
{
	radius = rad;
}//end ctor

double circle::getRadius()
{
	return rad;
}
//function to calculate circle area
double circle::area()const
{
	return rad * rad * 3.14;
}//end function to get circle area

//returns circle description
string circle::toString()const
{
  ostringstream os;
  os << getColor() <<" circle with radius of " << rad << " and area of " << area();
  return os.str();
}//end function to return circle description


#include <string>
using std::string;

#include <iostream>
using std::cout;
using std::cin;
using std::endl;

#include "circle.h"
#include "rectangle.h"
#include "square.h"


Shape* getShape()
{	


	int i;
	string shapetype;
	char choice;

	Shape* myShape[6];
	
	
	

	cout << "Creating a Shape  ";
	cout << "============================================== "<<endl;
	cout << " 1: Create a circle "<<endl;
	cout << " 2: Create a rectangle "<<endl;
	cout << " 3: Create a square "<<endl;
	cout << " 4: Done "<<endl;
	cout << "============================================== "<<endl;
	for ( i = 0; i < 6; ++i){
	cout << "Enter number for shapetype" <<endl;

	switch(choice){
	
	case '1':
	cout << "\nEnter the shape's color (or 'done')...";
	cin >>  s_color   ;
	cout << "\nEnter shape type..." ;
	cin >> shapetype;
	cout << "\nEnter radius... ";
	cin >> radius;
	myShape[i] = new circle(color, radius);
	break;
	
	case '2':
	cout << "\nEnter the shape's color (or 'done')...";
	cin >> color;
	cout << "\nEnter shape type...";
	cin >> shapetype;
	cout << "\nEnter the length and width...  ";
	cin >> width >> length;
	myShape[i] = new rectangle(color, length, width); 
	break;
	
	case '3':
	cout << "\nEnter the shape's color (or 'done')...";
	cin >> color;
	cout <<"\nEnter shape type...";
	cin >> shapetype;
	cout << "\nEnter the length of a side...";
	cin >> length;
	myShape[i] = new square(color, length);
	break;
	
	case '4':
	cout <<"\nEnter the shape's color (or 'done')...";
	cout << "done"<< endl;}

	}
	return myShape[i];

}

I try to run the function in int main(); with the function Shape* getShape(); but nothings comes up in the terminal.

 

[Mark44]

Shape* getShape()
{    
    int i;
    string shapetype;
    char choice;

    Shape* myShape[6];    

    cout << "Creating a Shape  ";
    cout << "============================================== "<<endl;
    cout << " 1: Create a circle "<<endl;
    cout << " 2: Create a rectangle "<<endl;
    cout << " 3: Create a square "<<endl;
    cout << " 4: Done "<<endl;
    cout << "============================================== "<<endl;
    for ( i = 0; i < 6; ++i){
    cout << "Enter number for shapetype" <<endl;

    switch(choice){    
        <snip -- deleted long switch statement>  
    }
    return myShape[i];
}

myShape is an array of 6 pointers to Shape objects. It's a local variable, meaning it has automatic duration. This is crucial for what you're trying to do. Right after your final return statement, myShape essentially dies off, This means that whatever address you've stored in the array, of a circle, or a rectangle, or whatever, the whole array is reclaimed, so the return statement just sends back garbage.

A better way to do things would be to pass a Shape object as a parameter to your getShape() function, and have this function construct the appropriate type of shape.