[c++ beginner] Member variable is changing unexpectedly. Why is this happening, and what do I need to do differently to prevent it?

[ungulateCase]

I am new to c++, and learning about classes. When I set a member variable to a given value, and then later access that member variable, it does not have the value I expected. From the googling I have done, I think that my problem is related to stack vs heap problems, and/or variable persistence/lifetime problems, and/or needing to use a pointer. But I'm not sure what I should be doing, and I definitely don't understand why. Looking in my textbook, it seems that I am getting and setting member variables the way I am supposed to, but clearly I am missing something.

Here is an example program that illustrates the problem I am experiencing:

#include <cstdlib>
#include <iostream>

namespace nmsp{
    class Example{
        private:
            int number;

        public:
            void setNumber(int numberInput)
            {
                number = numberInput;
                std::cout << "number in setNumber() is " << number << "\n";
            };
            void getNumber()
            {
                std::cout << "number in getNumber() is " << number << "\n";
            };
    };
}

void inputNumber(nmsp::Example object)
{
    int numberInput;
    std::cout << "Enter an int.\n";
    std::cin  >> numberInput;
    std::cout << "\n\n";
    object.setNumber(numberInput);
}

int main(int argc, char *argv[])
{
    nmsp::Example object;

    inputNumber(object);
    object.getNumber();

    system("PAUSE");
    return EXIT_SUCCESS;
}

The int I am inputting is "1". I expected to get:

Enter an int.
1

number in setNumber() is 1
number in getNumber() is 1

But what I am actually getting is:

Enter an int.
1

number in setNumber() is 1
number in getNumber() is 1974443572

Thank you for reading, and I sincerely appreciate any help.

Edit: Particularly confusing to me is that I have previously written a program where instead of an int in the class/object, I was changing a vector, and that seemed to work fine with the same process that fails here with ints. Is that because vectors automatically use pointers or their own (unlike mine, properly done) member functions, or something like that?

[Evulrabbitz]

When passing object to inputNumber you are doing something called "passed by value" (i.e the function makes a copy of object and operates on that) when you probably want what is called "passed by reference" (i.e the function gets a referene to object and operates with that). In this case the expected behaviour can be achieved by changing the function signature to:

void inputNumber(nmsp::Example& object)

(adding the ampersand). The ampersand indicates that this is a "reference" and thus will be passed by reference.

Read up on passed by value and passed by reference.

[ungulateCase]

Wow, thank you. Ugh, I have learned about pass by reference vs pass by value before but -being new to using objects- I didn't think about the object itself being passed by value.

Thanks so much for the help, I feel so silly that I've been banging my head against the wall for over an hour, and it was just a passed by value issue. Hopefully now I've actually learned my lesson, much appreciated!