Passing a class object as an argument in C++

Question

Suppose I had a class named foo containing mostly data and class bar that's used to display the data. So if I have object instance of foo named foobar, how would I pass it into bar::display()? Something like void bar::display(foobar &test)?

Solution 1

Yes, almost. Or, if possible, use a const reference to signal that the method is not going to modify the object passed as an argument.

class A;

class B
{
    // ...
    void some_method(const A& obj)
    {
        obj.do_something();
    }
    // ...
};

Solution 2

#include <iostream>

class Foo 
{
    int m_a[2];

    public:
    Foo(int a=10, int b=20) ;           
    void accessFooData() const;

};

Foo::Foo( int a, int b )
{
    m_a[0] = a;
    m_a[1] = b;
}

void Foo::accessFooData() const
{
    std::cout << "\n Foo Data:\t" << m_a[0] << "\t" << m_a[1] << std::endl;
}

class Bar 
{
    public:
    Bar( const Foo& obj );
};

Bar::Bar( const Foo& obj )
{
    obj.accessFooData();
   // i ) Since you are receiving a const reference, you can access only const member functions of obj. 
   // ii) Just having an obj instance, doesn't mean you have access to everything from here i.e., in this scope. It depends on the access specifiers. For example, m_a array cannot be accessed here since it is private.
}

int main( void )
{
    Foo objOne;
    Bar objTwo( objOne ) ;
    return 0 ;
}

Hope this helps.