Cannot call member function std::string class::function() without object

Question

I know it may seem like this has been asked before but I've looked around and the static method didn't work for me. Here's my code:

struct Customer {
public:
    string get_name();
private:
    string customer,first, last;
};

Here's where I call the function:

void creation::new_account() {
Customer::get_name(); //line it gives the error on.
}

Here's an example of some code that compiles fine.

struct Creation { public: string get_date(); private: string date; };

then I call it the same way

void Creation::new_account() { Creation::get_date();}

Hence my confusion why one works and the other doesn't.

EDIT: Ok I get it, I just realized I was calling a function of another struct inside a function definition that's part of a different class. I got it, thanks to all who answered

Answer 1

It is not declared static (needs to be static std::string get_name(); ). However, get_name() for Customer is a specific attribute of a Customer instance so having it static does not make sense, that is the same name for all instances of Customer . Declare an object of Customer and use it. It would make sense to have the name provided to the constructor of Customer , as surely a customer cannot exist without a name:

class Customer {
public:
    Customer(std::string a_first_name,
             std::string a_last_name) : first_name_(std::move(a_first_name)),
                                        last_name_(std::move(a_last_name)) {}
    std::string get_name();
private:
    std::string first_name_;
    std::string last_name_;
};

Declare an instance of Customer :

Customer c("stack", "overflow");
std::cout << c.get_name() << "\n";

Answer 2

Since your get_name is not declared static, it is a member function.

You probably need some constructors in your Customer class. Assuming you have some, you could code

 Customer cust1("foo123","John","Doe");
 string name1 = cust1.get_name();

You need an object (here cust1 ) to call its get_name member function (or method).

Time to spend many hours reading a good C++ programming book.

Answer 3

"The static method didn't work for me". It's not a method it's how the language works.

If you want to call some method without a concrete object, you need it to be static. Otherwise, you need an object.

Your code will work with one of the following :

struct Customer {
public:
    static string get_name();
private:
    string customer,first, last;
};

or

void creation::new_account() {
    Customer c;
    //stuff
    c.get_name();
}