Classes and Inheritance

[jdpjtp910]

Ok, I have a class project to basically design a program that handles classes and vehicles. What I have so far is far from the ending product. I have made 3 classes, car, vehicle, and motorcycle. Car and motorcycle are dervied from vehicle. The car class has a set const variable for number of wheels to 4. mpg and model name are the other variables. Motorcycle is a class with const for 2 wheels and model and mpg. Vehicle only has number of wheels and mpg.

Here is my code thus far.

Class: car.h

#ifndef CAR_H
#define CAR_H

#include <string>

#include "vehicle.h"

using std::string;

class Car  : public Vehicle {
public:
  Car();
  Car(string const& model, double milesPerGallon);

  void setModel(string const& model);

  string const& getModel() const;

  virtual void print() const;

private:
  string model;
};

#endif 

motorcycle.h:

#ifndef MOTORCYCLE_H
#define MOTORCYCLE_H

#include <string>

#include "vehicle.h"

using std::string;

class MotorCycle : public Vehicle {
public:
  MotorCycle();
  MotorCycle(string const& model, double milesPerGallon);

  void setModel(string const& model);

  string const& getModel() const;

  virtual void print() const;

private:
  string model;
};

#endif 

vehicle.h:

#ifndef VEHICLE_H
#define VEHICLE_H

class Vehicle {
public:
  Vehicle();
  Vehicle(int wheels, double milesPerGallon);

  void setWheels(int wheels);
  void setMilesPerGallon(double milesPerGallon);

  double getMilesPerGallon() const;
  int    getWheels() const;

  virtual void print() const;

private:
  int wheels;
  double milesPerGallon;
};

#endif 

car.cpp:

#include "car.h"

#include <iostream>

using namespace std;

Car::Car() {
}

Car::Car(string const& model, double milesPerGallon)
    : Vehicle(4, milesPerGallon), model(model) {
}

void Car::setModel(string const& model) {
  this->model = model;
}

string const& Car::getModel() const {
  return model;
}

void Car::print() const {
  Vehicle::print();
  cout << "Car model: " << model << "\n";
}

motorcycle.cpp:

#include "motorcycle.h"

#include <iostream>

using namespace std;

MotorCycle::MotorCycle() {
}

MotorCycle::MotorCycle(string const& model, double milesPerGallon)
    : Vehicle(2, milesPerGallon), model(model) {
}

void MotorCycle::setModel(string const& model) {
  this->model = model;
}

string const& MotorCycle::getModel() const {
  return model;
}

void MotorCycle::print() const {
  Vehicle::print();
  cout << "Motorcycle model: " << model << "\n";
}

vehicle.cpp:

#include "vehicle.h"

#include <iostream>

using namespace std;

Vehicle::Vehicle() {
  wheels = 0; milesPerGallon = 0;
}

Vehicle::Vehicle(int wheels, double milesPerGallon)
  : wheels(wheels), milesPerGallon(milesPerGallon) {
}

void Vehicle::setWheels(int wheels) {
  this->wheels = wheels;
}

void Vehicle::setMilesPerGallon(double milesPerGallon) {
  this->milesPerGallon = milesPerGallon;
}

double Vehicle::getMilesPerGallon() const {
  return milesPerGallon;
}

int Vehicle::getWheels() const {
  return wheels;
}

void Vehicle::print() const {
  cout << "Wheels number: " << wheels << "\n"
    << "Miles per gallon: " << milesPerGallon << "\n";
}

main.cpp:

#include <iostream>

#include "car.h"
#include "vehicle.h"
#include "motorcycle.h"

using namespace std;

int main() {
  double mpg; 
  int wheelss;
  Car c("Ford", 8);
  MotorCycle mc("Bike", 5);
  

  
  cout << "Please enter the miles per gallon for vehicle:" << endl;
  cin >> mpg;
  Vehicle milesPerGallon(double mpg);
  cout << "Please enter the number of wheels for the vehicle:" << endl;
   cin >> wheelss;
  Vehicle wheels(int wheelss);

 
  Vehicle.print();
  c.print();
  mc.print();

  return 0;
}

Problem I am having is getting users to input the code instead of having it statically held by the program. So i am attempting this with the vehicle class. I am prompting for mpg and number of wheels. when I compile I get the follow error:
Error 1 error C2143: syntax error : missing ';' before '.' \Desktop\vehicle\main.cpp 25 test15
Error 2 error C2143: syntax error : missing ';' before '.' \Desktop\vehicle\main.cpp 25 test15

I tried googleing the error and found that it typically has something to do with omission in previos lines. I have checked previous lines and have semi colons through out. Any help/guidance would be great.

THank you in advance for your time and effort!

[denis90]

In order to get the previous list of code to compile you have to remove the line

Vehicle.print();

Anyways there are lots of misconceptions in your code, this is one of those. You're actually calling the print() which is non-static member of Vehicle without referring to any object. In order to make a call to a non-static member function you always need an object to call that function from, just like you did in:

 c.print();
 mc.print();

Applying the concept to a real life example, what you did there (Vehicle.print();) is like tying to pump up the tyres (well, this would have been a different function but you got the idea) of a non-existing vehicle, quite of an impossible task, isn't it?


This part is also quite weird:

  cout << "Please enter the miles per gallon for vehicle:" << endl;
  cin >> mpg;
  Vehicle milesPerGallon(double mpg);
  cout << "Please enter the number of wheels for the vehicle:" << endl;
   cin >> wheelss;
  Vehicle wheels(int wheelss);

First of all we have some syntax problems: calling the constructor of a class is like calling any other function, furthermore mpg and wheelss have already been declared, therefore writing Vehicle milesPerGallon(double mpg); or Vehicle wheels(int wheelss); is wrong!
Instead you should have written:

  cout << "Please enter the miles per gallon for vehicle:" << endl;
  cin >> mpg;
  Vehicle milesPerGallon(mpg);
  cout << "Please enter the number of wheels for the vehicle:" << endl;
   cin >> wheelss;
  Vehicle wheels(wheelss);

Anyways, apart from the syntax, there is a logical misconception here: how the heck can milesPerGallon or wheelss be vehicles? Try to think it over, that doesn't make any sense.

Hope it helped out! ;)