Calculate class Cylinder using class Circle

Question

The constructor of class "Circle" allows the radius to be specified via a parameter, while it is not possible to create objects of the Circle type without specifying the parameter. Also, automatic conversion of real numbers into Circle objects must not be allowed. The Set method, which does the same thing as a constructor, should also be supported, except that it allows the radius of an already created object to be changed later.

The Cylinder class constructor requires two parameters that represent the base radius and the height of the roller, respectively. Instances of this class also cannot be created without specifying the mentioned information. It should also support the "Set" function, which does the same thing as a constructor, except that it allows you to modify an already created object.

Both classes must have other methods (listed in code).

I need to use class Circle inside class Cylinder to enable calculating volume, area, and other functions.

#include <cmath>
#include <iostream>

class Circle {
  double radius;

  public:
  Circle(double r);
  void Set(double r);
  double GetRadius() const;
  double GetPerimeter() const;
  double GetArea() const;
  void Scale(double s);
  void Print() const;
};

class Cylinder {
  Circle baze;
  double height;

  public:
  Cylinder(double r_baze, double h);
  void Set(double r_baze, double h);
  Circle GetBaze() const;
  double GetRadiusOfBaze() const;
  double GetHeight() const;
  double GetArea() const;
  double GetVolume() const;
  void Scale(double s);
  void Print() const;
};

int main() { 
  return 0; 
}

Circle::Circle(double r) {
  radius = r;
}

void Circle::Set(double r) {
  radius = r;
}

double Circle::GetRadius() const { return radius; }

double Circle::GetPerimeter() const { return 2 * 4 * atan(1) * radius; }

double Circle::GetArea() const { return radius * radius * 4 * atan(1); }

void Circle::Scale(double s) {
  radius *= s;
}

void Circle::Print() const {
  std::cout << "R= " << GetRadius() << " O= " << GetPerimeter()
            << " P= " << GetRadius();
}

Cylinder::Cylinder(double r_baze, double h) {
  baze.GetRadius() = r_baze;
  height = h;
}

void Cylinder::Set(double r_baze, double h) {
  baze.GetRadius() = r_baze;
  height = h;
}

Circle Cylinder::GetBaze() const { return baze; }

double Cylinder::GetRadiusOfBaze() const { return baze.GetRadius(); }

double Cylinder::GetHeight() const { return height; }

double Cylinder::GetArea() const {
  return baze.GetArea() * 2 + baze.GetPerimeter() * height;
}

double Cylinder::GetVolume() const { return baze.GetArea() * height; }

void Cylinder::Scale(double s) {
  baze.GetRadius() *= s;
  height *= s;
}

void Cylinder::Print() const {
  std::cout << "R= " << baze.GetRadiusOfBaze() << " H= " << height
            << " P= " << GetArea() << " V= " << GetVolume();
}

I'm new to objected-oriented programming concept. Could you help me to understand where I'm making mistakes?

I cannot compile this, because I get errors:

57 : no matching function for call to ‘Circle::Circle()’

14: note: candidate: ‘Circle::Circle(double)’

14: note: candidate expects 1 argument, 0 provided

3: note: candidate: ‘constexpr Circle::Circle(const Circle&)’

3: note: candidate expects 1 argument, 0 provided

62, 70, 91 : lvalue required as left operand of assignment

***because I get some errors*** What errors? Please edit your question and add the exact text of the error messages. — drescherjm, May 23 '22 at 22:41
For the first error "no matching function for call to ‘Circle::Circle()’" you need this: [https://stackoverflow.com/questions/1711990/what-is-this-weird-colon-member-syntax-in-the-constructor](https://stackoverflow.com/questions/1711990/what-is-this-weird-colon-member-syntax-in-the-constructor) — drescherjm, May 23 '22 at 22:55
Also, the `GetRadius()` function is for reading the value, not for changing it. Hint: There is also a `Set()` function. — BoP, May 23 '22 at 23:06
Is the assignment missing the location parameters, such as `x,y` in Cartesian Coordinate System? — Thomas Matthews, May 23 '22 at 23:36
You may simplify your code by having `Cylinder` inherit from `Circle`. In one view, a cylinder has all the same methods and members that a circle does. On the other hand, a Cylinder is made up of (contains) an infinite quantity of circles. — Thomas Matthews, May 23 '22 at 23:39
@ThomasMatthews Task doesn't say anything about x and y coordinates, this doesn't require that. This is simple circle and cylinder. — cpp_mountain, May 24 '22 at 01:31
@BoP in function `Set` I don't know how to access radius of baze, that's problem... radius of class Circle is private, so I cannot access with `baze.radius` I should access it with function `GetRadius` — cpp_mountain, May 24 '22 at 11:45
`baze` has its own `Set` function. Just call that from the derived class. — BoP, May 24 '22 at 12:01

Chris · Accepted Answer · 2022-05-23T23:28:28.587

1

Cylinder::Cylinder(double r_baze, double h) {
 baze.GetRadius() = r_baze;
 height = h;
}

In your Cylinder class, when your constructor is called, baze is implicitly initialized with a default constructor that does not exist.

You want to use an initializer list to handle that initialization, at which point the code inside your Cylinder constructor becomes unnecessary.

Cylinder::Cylinder(double r_baze, double h) 
: baze(r_baze), height(h) {
}

Alternatively, you could provide functionally a default constructor for your Circle class, and then Set the radius in Cylinder's constructor, but that's more work.

Circle::Circle(double r=0.0) {
  radius = r;
}

Cylinder::Cylinder(double r_baze, double h) {
  baze.Set(r_baze);
  height = h;
}

Also...

Please note that GetRadius returns a double and cannot be assigned to, so you will get an error on that line of code.

edited May 23 '22 at 23:28

answered May 23 '22 at 23:22

Chris

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thank you very much, do you know how could I make this `baze.GetRadius() = r_baze;` and `baze.GetRadius() *= s;` work? How to access radius of baze using function GetRadius(), is there any way to use reference for that? – cpp_mountain May 24 '22 at 01:29
or pointer `this`? – cpp_mountain May 24 '22 at 01:35
@drescherjm It has, look at the code `void Cylinder::Set(double r_baze, double h)` but I have problem with that, I cannot access radius of baze, I don't know how to access it... – cpp_mountain May 24 '22 at 11:40

Calculate class Cylinder using class Circle

1 Answers1