c ++指向另一个类错误的指针“没有运算符匹配这些操作数。”

Question

edit* I'm dumb... Thanks for helping me this question is solved. * In my car class the code below keeps giving me an error on the << operators

cout << "Driver: " << driver->print(); 
cout << "Owner: " << owner->print();

The error says "no operator matches these operands." This is my homework assignment so I do need to somehow from the driver call the print function. In the main function I'm not actually setting the driver or owner yet but that shouldn't matter I wouldn't think. Thanks in advance.

#include <iostream>
#include <string>
#include <vector>

using namespace std;

class Person
{
public:
Person(string _name,int _age)
{
    _name = name;
    _age = age;
    cout << "Name: " << name << endl;
    cout << "Age: " << age << endl;
}
string getName()
{
    return name;
}
int getAge()
{
    return age;
}
int incrementAge()
{
    age +=1;
    return age;
}
void print()
{
    cout << "Name: " << name << endl;
    cout << "Age: " << age << endl;

}


private:
string name;
int age;

};

class Car
{
public:
Car (string m)
{
    model = m;
}
void setDriver(Person *d)
{
    *driver = *d;
}
void setOwner(Person *o)
{
    *owner = *o;
}
void print()
{
    cout << "Model: " << model << endl;
    cout << "Driver: " << driver->print();
    cout << "Owner: " << owner->print();
}




private:

string model;
Person *owner;
Person *driver;


};

int main()
{
vector<Person*>people;
vector<Car*>cars;
string name = "";
int age = 0;
string model = 0;
int sentValue = 0;
while (sentValue != -1)
{
    cout << "Enter name: ";
    cin >> name;
    cout << "Enter age: ";
    cin >> age;


    people.push_back(new Person(name, age));
    cout << "Enter car model: ";
    cin >> model;
            cars.push_back(new Car(model));
    cout << "Press -1 to stop, or 1 to enter info for others: ";
    cin >> sentValue;
}






//display car model, 
//owner’s name and age,
//and driver’s name and age.

system("pause");
return 0;
   }

Answer 1

The C++ way of doing this would be to implement std::ostream&<< operators for Person and Car . For example,

#include <iostream>

std::ostream& operator<<(std::ostream& o, const Person& p) {
  return o << "Name: " << p.getName() << " Age: " << p.getAge();
}

then use like this:

Person p("Bob", 23);
std::cout << p << "\n";

As an aside, I don't think you really need all those pointers in your code.

Answer 2

Your print() function already sends the output to cout , so there is no need to try to send it there again. Instead of

cout << "Driver: " << driver->print(); 

you probably want

cout << "Driver:" << endl;
driver->print();

Answer 3

The member functions print return void . You can't insert a void into a stream. If you change the print functions to take a stream reference and add overloaded operators that call print, you can just insert the objects themselves into the stream; that would be more idiomatic.

template <class Elem, class Traits>
void Car::print(std::ostream<Elem, Traits>& out) {
    out << "Model: " << model << '\n';
    out << "Driver: " << *driver;
    out << "Owner: " << *owner;
}

template <class Elem, class Traits>
std::ostream<Elem, Traits>& out, const Car& car) {
    return out << car;
}

Answer 4

cout << "Driver: " << driver->print(); 

your << waiting for an appropriate object to process. That is your problem. Rather than implementing print() , overload the operator by implementing operator<<(std::ostream&, const Person&); and let the C++ do the rest. Then you can print like that:

 cout << "Driver: " << driver; 

Answer 5

const std::string& Person::print() const
{
    return "Name " + name + "\n" + "Age " + age + "\n";    
}