Modifying the Contained Members

Section 17.8 Modifying the Contained Members

The same logic applies if want to add functions to change the location of a Circle - it does directly control the data (x and y) that needs to be changed. So any function that needs to modify those values will need to rely on calling methods on m_center.

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This is demonstrated in the sample below. Note that setRadius can directly do the needed work as the m_radius variable is “owned” directly by the Circle. However setX() and setY() need to ask m_center to make the needed changes:

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Listing 17.8.1.

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#include <iostream>
//import the Point class
import Point;

using namespace std;

class Circle {
public:
    Circle(double radius, double x, double y) {
        m_radius = radius;
        m_center = Point(x, y);
    }

void setRadius(double radius) {
        // Can directly set the radius
        m_radius = radius;
    }

void setX(double x) {
        // Need to use the Point class to set the x-coordinate of the center
        m_center.setX(x);
    }

void setY(double y) {
      // Need to use the Point class to set the y-coordinate of the center
        m_center.setY(y);
    }

double getRadius() const {
        return m_radius;
    }

double getX() const {
        return m_center.getX();
    }

double getY() const {
        return m_center.getY();
    }

private:
    double m_radius;
    Point m_center;
};

int main() {
    Circle c1(5.0, 2, 1);
    c1.setRadius(10.0);
    c1.setX(3.0);
    c1.setY(-4.0);
    cout << c1.getRadius() << endl;
    cout << c1.getX() << endl;
    cout << c1.getY() << endl;
}

Checkpoint 17.8.1.

Class Address has a m_streetAddress, m_city, and m_zip. Class Contact is shown below. If a Contact is asked to do the following tasks, which ones sound like they should be handed off to the m_address to do?

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class Contact {
  public:
      ...
  
  private:
      string m_name;
      string m_email;
      Address m_address;
  };

Check if the contact is in a particular city.
Update the contact’s street address.
Get the address of the contact in the format “123 Main, Town 12345”.
Get the contact’s name
Update the contact’s email

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