Class Reference Problem

[tvborda]

Hi everyone, im new to C++ and i'm having a few problems with reference.

Here is my example.

Foo.h

class Foo {
  private:
    int myA = 0;
    int myB = 0;
  public:
    Foo(int a, int b);
    int print_plus();
}

Foo.cpp

Foo::Foo(int a, int b) {
  myA = a;
  myB = b;
}
Foo::print_plus() {
  printf("a+b=%i", myA + myB);
}

myApp.cpp

#include <iostream>
using namespace std;

Foo f;   // Here is the doubt, how to just make a reference, not initialize.

int main() {
  printf("Starting Foo!");
  f(4,5); // Here i want to initalize the object.
  anotherFunc();       // And use it anywhere.
  otherAnotherFunc();  // Here too.
}

int anotherFunc() {
  f.print_plus();
}

int otherAnotherFunc() {
  f.print_plus();
}

So my problem is that i know that my Foo class don't have a constructor that accept no parameters, so in "Foo f" statement the compiler complains.

Of course this is just an example my program is a little more complicated, but the issue is the same, how to make a reference to further use on other class or function.

Thanks, Thiago.

[firedraco]

Well...the way you seem to be trying is making a global variable as opposed to a reference...

Here is an example of a reference and how it is different:

void increase(int myInt) {
   ++myInt;
} //this function doesn't actually increase the int you pass, it increases a copy
//of it, which is destroyed when the function returns

void real_increase(int &myInt) { //passing by reference
   ++myInt;
} //this actually does increase the actual variable, since you are passing the
//reference instead of a copy 

[tvborda]

I just realize what i was trying to do. The command that i was looking is the "new". Most of high level languages control the pointers by itself.

Here is what i wanted to do:

#include <iostream>
using namespace std;

Foo *f; // Pointer to future object.

int main() {
  printf("Starting Foo!");
  f = new Foo(4,5); // Here i initalize the object with the new.
  anotherFunc();       // And use it anywhere.
  otherAnotherFunc();  // Here too.
}

int anotherFunc() {
  f->print_plus();
}

int otherAnotherFunc() {
  f->print_plus();
}

Thanks everybody, thanks Firedraco.