Hi the code below is a simple class example in C

#include <iostream>
using namespace std;

class Car {        // The class
  public:          // Access specifier
    string brand;  // Attribute
    string model;  // Attribute
    int year;      // Attribute
    Car(string x, string y, int z) {  // Constructor with parameters
      brand = x;
      model = y;
      year = z;
    }
};

int main() {
  // Create Car objects and call the constructor with different values
  Car carObj1("BMW", "X5", 1999);
  Car carObj2("Ford", "Mustang", 1969);

  // Print values
  cout << carObj1.brand << " " << carObj1.model << " " << carObj1.year << "\n";
  cout << carObj2.brand << " " << carObj2.model << " " << carObj2.year << "\n";
  return 0;
}
// W3Schools

As I see it, the way you can define an object is to write it in code like : <ClassName> <ObjectName>

Now my question is : Is there a way to input an object? like cin >> ObjectName;

And after we entered the name of object, we enter the parameters.

Is it possible at all?

CodePudding user response：

You can't enter an object name from the command line, however, you can create a default constructed object and then fill its' properties from the input by overloading operator>>.

class Car {
  public:
    Car() = default;
    // ...
};

std::istream& operator>>(std::istream& in, Car& car) {
  in >> car.brand >> car.model >> car.year;
  return in;
}

int main() {
  Car carObj1;
  cout << "Enter a car brand, model, and year: ";
  cin >> carObj1;
  // ...
}

CodePudding user response：

Yes, There is operator overloading in C and you can overload both << and >> operators. Here is an example code:

#include <iostream>
using namespace std;

class Car {        // The class
  public:          // Access specifier
    string brand;  // Attribute
    string model;  // Attribute
    int year;      // Attribute
    Car(string x, string y, int z) {  // Constructor with parameters
      brand = x;
      model = y;
      year = z;
    }

    Car() = default;

    void Carinput(std::istream& is)
    {
        is >> brand >> model >> year;
    }

    void carOutput(std::ostream& os) const
    {
        os << brand << " " << model << " " << year << std::endl;
    }
};

std::istream &operator>>(std::istream &is,Car &car)
{
    car.Carinput(is);
    return is;
}

std::ostream &operator<<(std::ostream &os,const Car &car)
{
    car.carOutput(os);
    return os;
}

int main() {
  // Create Car objects and call the constructor with different values
  Car carObj1("BMW", "X5", 1999);
  Car carObj2("Ford", "Mustang", 1969);

  // Print values
  cout << carObj1.brand << " " << carObj1.model << " " << carObj1.year << "\n";
  cout << carObj2.brand << " " << carObj2.model << " " << carObj2.year << "\n";

  std::cout << "\n*============================================*\n"
            << std::endl;

  std::cout << "Your input:" << std::endl;
  Car carObj3;
  std::cin >> carObj3;
  std::cout << carObj3;

  return 0;
}

CodePudding user response：

This is one of the ways of doing it:

#include<iostream>
#include<vector>


class Car
{
public:
    Car( const std::string& brand, const std::string& model, int year )
    : m_brand( brand ), m_model( model ), m_year( year ) // initialize members like this
    {
    }

    std::string m_brand;
    std::string m_model;
    int m_year;
};

int main ()
{
    std::vector< Car > cars; // use an std::vector to store the objects
    std::string brand( "" );
    std::string model( "" );
    std::string year( "" );
    

    std::cout << "How many cars do you want to add? ";
    std::string count( "" );
    std::getline( std::cin, count ); // get input as string using std::getline()
    int carCount { std::stoi( count ) }; // converts it to type int before 
                                         // assigning it to carCount

    cars.reserve( carCount ); // reserve some space in vector to avoid 
                              // unnecessary allocations and slowdowns

    for ( int idx = 0; idx < carCount;   idx )
    {
        std::cout << "Enter the brand name of car number " << idx   1 << ": ";
        std::getline( std::cin, brand );

        std::cout << "Enter the model name of car number " << idx   1 << ": ";
        std::getline( std::cin, model );

        std::cout << "Enter the production year of car number " << idx   1 << ": ";
        std::getline( std::cin, year );

        cars.emplace_back( Car( brand, model, std::stoi( year ) ) ); // push the new Car
    }                                                                // instance to the
                                                                     // vector called cars
    std::cout << '\n';

    for ( int idx = 0; idx < carCount;   idx )
    {
        std::cout << "Info for car number " << idx   1 << ": "
        << cars[ idx ].m_brand << " " << cars[ idx ].m_model << " " << cars[ idx ].m_year << "\n";
    }
    return 0;
}

Here is the output:

How many cars do you want to add? 2
Enter the brand name of car number 1: Porsche
Enter the model name of car number 1: GT3 RS
Enter the production year of car number 1: 2019
Enter the brand name of car number 2: BMW
Enter the model name of car number 2: M6
Enter the production year of car number 2: 2016

Info for car number 1: Porsche GT3 RS 2019
Info for car number 2: BMW M6 2016

But keep in mind that this class still needs a lot of work like adding member functions (like getters and setters) etc. So this is not how I write classes. I just wanted to keep it simple so you can easily understand the concepts.