Extraction operator overloading confusion!

[BambiWithPMS]

Hi all!

I have been stuck on extraction overloading for hours now and the error code i get is "All paths through this function will call itself" if that helps!

istream& operator>>( istream& is, const Measurement& content){
    
    is >> content.feet >> content.inch;
    return is;
}

This is my extraction overload header and I have two private variable 'feet' and 'inch' of type int.

Measurement::Measurement(int x){
    setFeet(x);
    setInch(x);
}

Measurement::Measurement(Measurement& x){ //Copy constructor
    feet = x.feet;
    inch = x.inch;
}

Measurement::Measurement(){} //Empty parameter constructor 

Here are my constructors.

The line in my main.cpp is simply 'cin << obj;'

Any hints?
Thank you!

[Ganado]

I assume you mean "cin >> obj;".

Why don't you tell us where the error says its happening? The more information you can provide us, the better chance we have of helping you.

I don't see anything immediately wrong with what you have provided. Perhaps post more context?

[mbozzi]

"All paths through this function will call itself"

I can't see why. Are you sure that error comes from this part of the code?

Anyways, you can't modify (the referent of) content because it's a reference to const. Get rid of it:

istream& operator>>( istream& is, /* const */ Measurement& content) 
{ return is >> content.feet >> content.inch; } 

The line in my main.cpp is simply 'cin << obj;'

Ought to be cin >> obj.

The arrow points in the direction the data moves - in this case, from std::cin into obj.

For example:

#include <iostream>

struct measurement {
  int feet, inch;
};

std::istream &operator>>(std::istream &s, measurement &m) {
  return s >> m.feet >> m.inch;
}

int main() { measurement obj; std::cin >> obj; }

Also, your copy constructor shouldn't be there: best practice is to not write special member functions yourself unless they are required; they are only required when the class directly manages a resource - memory, for example. This is called the rule of zero:
http://en.cppreference.com/w/cpp/language/rule_of_three

It also really should have

Measurement::Measurement(Measurement const & x)

so that you can copy const objects.

[BambiWithPMS]

Thanks for the reply guys! Sorry about the late response.

I actually experimented with the header after I posted my post and actually solved it.

I took out the 'const' in the extraction operator header and it worked!!

So i looks like this,

istream& operator>>( istream& is, Measurement& content){
    
    is >> content.feet >> content.inch;
    return is;
}

Now, I don't understand why that works though since I am still confused about the purpose of 'const'.

[Ganado]

const means that it's an object that cannot be modified after being initially set. You're trying to put information into content.feet and content.inch, which are part of your content object; this cannot be done if content is const.