Thread: Retrieving a varible from a different function

Pass as a parameter, or return it as a result.

>What I would like to do is have "function a" use "variable b" which is stored in "function c".
If "function a" needs "variable b" then why is it stored in "function c"? Wouldn't it make more sense for both function a and c to be member functions in a class where variable b is a data member? It sounds to me like your design needs a refit rather than a kludge.

Read the tutorials on this website about functions lilrayray... pretty please

You saw this? http://www.cprogramming.com/tutorial/lesson4.html

error: new types may not be defined in a return type

I think this means that you have as the return type of a function "class foo", and class foo has not been declared.

Hint: static variables/functions.

A static variable is a variable that exists only once for every instance of the class; a static method can access such static variables.

Code:

class c {
private:
    static int x;

public:
    int get_x() { return x; }
    void set_x(int t) { x = t; }
};

void function() {
    c::set_x(5);
    cout << c::get_x();
}

or

Code:

class c {
public:
    static int x;
};

void function() {
    c::x = 5;
    cout << c::x;
}

You could use a structure instead of a class for the second example, which would allow you to drop the "public:".

[edit]
Constructors and destructors are special methods called every time an instance of the inclosing class is created or destoyed, respectively. You don't need to use them for a class that only has static variables.
[/edit]

[edit=2]
To give an initial value to a static variable, try this:

Code:

class c {
public:
    static int x;
};

int c::x = 5;

[/edit]

i take it you just prefer to ask us intead of reading the tutorials right?

"What the heck! Why should I do all the work. Let someone answer my doubts while I sit here calmly waiting. Searching is for those nerds who like to know everything"

A member function is used with the help of the member access operator.

Code:

t myObject;
myObject.test(); // <-- this is how you use it

Constructors are ran when you instantiate an object of your class. They are usually used to initialize data membrs and do some administrative tasks.

Destructors are ran when the object of the class dies (goes out of scope or is explicitely deleted). Usually they are used to do some cleaning up.

For something as simple as a variable that can be accessed from two functions, you probably don't need a class. As mentioned, pass arguments:

Code:

void print(int x) {
    cout << x;
}

Or return values:

Code:

void get() {
    int x;
    cin >> x;
    return x;
}

Or pass references to see your changes:

Code:

#include <iostream>

using std::cout;
using std::endl;

void add(int x) {
    x ++;
}

void addref(int &x) {
    x ++;
}

int main(void) {
    int x = 5;

    cout << x << endl;
    add(x);
    cout << x << endl;
    addref(x);
    cout << x << endl;

    return 0;
}

Output:

Code:

5
5
6

As you can see, if you pass a regular variable, the function gets a local copy of it and can do what it wants to it. It you want the changes to be reflected, return the variable after you've modified it, or pass a reference/pointer.