Member variables

Learn to declare member variables (fields) in a class.

Member variables

Variables declared in a class body are called member variables. They hold the object's data. In a Product class, std::string name; is a member variable.

Member variables take an access modifier: public from anywhere, private only inside the class. For now we use public so we can access them directly from outside. Member names start lowercase: name, price, stock.

Accessing members

You access a public member of an object with a dot: product.name. Assignment works the same way: product.name = "Pen";. You must declare the object first; you cannot access members before that.

A member variable may hold a garbage value at first. So it is good practice to assign values right after creating the object. std::string starts as an empty string by default, but types like int have undefined content until you assign one.

Exercise Add member variables to the Product class

Define a Product class. Under public: add std::string name; and int stock; member variables. In main create an instance, set name to "Pen" and print name with std::cout.

Show example solution

#include <iostream>
#include <string>

class Product {
public:
    std::string name;
    int stock;
};

int main() {
    Product product;
    product.name = "Pen";
    std::cout << product.name;
    return 0;
}

Test yourself

Complete the member declaration

class Product { public: std::string ____; };

Show answer

class Product { public: std::string name; };

How do you access product.price?
```
Product product;
```
- product.price
- product->price
- product::price
- product#price
Show answer

product.price — The dot accesses a member of a stack object.
Match each declaration to its type

std::string name;

Member variable
class Product { };

Class definition
Product product;

Instance creation
product.name

Member access

Next lesson: Member functions

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