为什么我在类 function 中使用 objet 时会出现未声明的标识符错误？

Question

I've been self teaching CPP OOP and this error occurred: Error C2065 'carObj1': undeclared identifier

And since I'm self teaching I tried to search on Inte.net but nothing found? Can anyone help me with this?

#include <iostream>
#include <string>
using namespace std;

class car {
    public:
        string brand;
        string model;
        int year;
        void enterCar() {
            cout << "\nYour car is:" << carObj1.brand << " MODEL:" << carObj1.model << " BUILT-IN:" << carObj1.year;

        }
};

int main()
{
    car carObj1;

    cout << "Enter your car's brand name:\n";
    cin >> carObj1.brand;

    cout << "Enter your car's Model:\n";
    cin >> carObj1.model;

    cout << "Enter your car's Built-in year:\n";
    cin >> carObj1.year;

    carObj1.enterCar();



    return 0;

}

Answer 1

The problem is that you're trying to access the fields brand , model and year on an object named carObj1 which isn't there in the context of the member function car::enterObj .

To solve this you can either remove the name carObj1 so that the implicit this pointer can be used or you can explicitly use the this pointer as shown below:

void enterCar() {
//-------------------------------------------vvvvv-------------->equivalent to writing `this->brand`
            std::cout << "\nYour car is:" << brand <<std::endl;
//-----------------------------------vvvvvv------------------->explicitly use this pointer
            std::cout<< " MODEL:" << this->model << std::endl;
            std::cout<<" BUILT-IN:" << this->year;

        }

Also i would recommend learning C++ using a good C++ book .