How to print class object using operator<< - c++

Question

I want to write a print function for a class AutoData that has information about cars in it. With this print function, I would ideally like to print out a vector that contains many different class objects. I have already written get functions for each element of the objects, but I am still a bit unsure of how to go about using those to write a function to print out the data in the following format:
mpg:cylinders:displacement:horsepower:weight:acceleration:modelYear:origin:carName
For example:
10.0:8:360.0:215.0:4615.:14.0:70:1:ford f250
10.0:8:307.0:200.0:4376.:15.0:70:1:chevy c20
11.0:8:318.0:210.0:4382.:13.5:70:1:dodge d200
The class is:
#include <string>
#include <vector>
#include <iostream>
using namespace std;
class AutoData {
public:
AutoData()
{
mpg = 0;
cylinders = 0;
displacement = 0;
horsepower = 0;
weight = 0;
acceleration = 0;
modelYear = 0;
origin = 0;
carName = "";
}
AutoData( const AutoData & rhs)
{
setAuto(rhs.mpg, rhs.cylinders, rhs.displacement, rhs.horsepower, rhs.weight, rhs.acceleration, rhs.modelYear, rhs.origin, rhs.carName);
}
void setAuto(float mp, int cy, float di, float ho, float we, float ac, int mo, int o, string ca)
{
mpg = mp;
cylinders = cy;
displacement = di;
horsepower = ho;
weight = we;
acceleration = ac;
modelYear = mo;
origin = o;
carName = ca;
}
const float & getmpg( ) const
{
return mpg;
}
const int & getcylinders( ) const
{
return cylinders;
}
const float & getdisplacement( ) const
{
return displacement;
}
const float & gethorsepower( ) const
{
return horsepower;
}
const float & getweight( ) const
{
return weight;
}
const float & getacceleration( ) const
{
return acceleration;
}
const int & getmodelYear( ) const
{
return modelYear;
}
const int & getorigin( ) const
{
return origin;
}
const string & getcarName( ) const
{
return carName;
}
bool operator == (const AutoData & rhs ) const
{
if( getmpg( ) == rhs.getmpg( ) )
{
return gethorsepower( ) == rhs.gethorsepower( );
}
else
{
return false;
}
}
bool operator > ( const AutoData & rhs ) const
{
if( rhs.getmpg( ) > getmpg( ) )
{
return true;
}
else if( getmpg( ) == rhs.getmpg( ) )
{
if( rhs.gethorsepower( ) > gethorsepower( ) )
{
return true;
}
}
else
{
return false;
}
}
private:
float mpg;
int cylinders;
float displacement;
float horsepower;
float weight;
float acceleration;
int modelYear;
int origin;
string carName;
};
Any help/advice anyone can provide would be very much appreciated!! Thanks

Answer 1

If you want to be able to do std::cout << AutoData();, you need to overload the output stream operator operator<<:
std::ostream& operator<< (std::ostream &out, AutoData const& data) {
out << data.getmpg() << ':';
out << data.getcylinders() << ':';
// and so on...
return out;
}
This function is not a member function, and since you have getters for each attribute, you do not have to declare this function as friend of your class.
Then you can do:
AutoData myAuto;
std::cout << myAuto << '\n';

Answer 2

What have you tried so far? My approach would be overloading operator<<, like:
std::ostream& operator<<(std::ostream& out, const AutoData& dasAuto) {
return out << dasAuto.getmpg() << ':' << dasAuto.getcylinders() <<
/* insert everthing in the desired order here */
std::endl;
}
And the same thing for the "reading" function, like:
std::istream& operator>>(std::istream& in, AutoData& dasAuto) {
float mpg;
int cylinders;
float displacement;
float horsepower;
float weight;
float acceleration;
int modelYear;
int origin;
string carName;
char separator;
const char SEP = ':';
if( !(in >> mpg >> separator) || (separator != SEP) ) return in;
if( !(in >> cylinders >> separator) || (separator != SEP) ) return in;
/* rinse, repeat */
if( !std::getline(in, carName) ) return in;
dasAuto.setAuto(mpg, cylinders /*, etc etc */);
return in;
}

Answer 3

You can read this artical to know about friend and operator <<,
http://www.cprogramming.com/tutorial/friends.html
In the class AutoData, you should declare this function:
friend ostream& operator<< (ostream& out, const AutoData& obj);
outside the class, you should define this function like this:
ostream& operator<< (ostream& out, const AutoData& obj)
{
out<<obj.mpg<<":";
//do what you want
return out;
}