Operator bitwise left shift

Question

What is the recommended approach for updating an object after creation with a stream of data? I would like to avoid using a number of SetXX methods.

Say I have a class that looks like this;

class Model
{
public:
  Model(int, double, std::string);
private:
  int a;
  double b;
  std::string c;
};

One approach to solving this was adding operator;

friend Model& operator<<(Model&, std::stringstream&)

The usage of the above code;

// create model
Model model(...);

// do stuff

// update model later
model << stream;

This approach compile and runs.

Just wondering if this is a good approach and if it has any flaws \\ limitations? Notice that most example online using operator<< use it differently than what I am doing above.

Answer 1

I would suggest to follow the same notation as in the standard library: use operator>> for input and return reference to the stream, not the Model . This way it will be more readable for the others (who are familiar with the standard library but not your notation), and it will allow for chained inputs:

friend std::istream & operator>>(std::istream & s, Model & m)
{
    m.data = ...
    return s;
}

Model m1, m2;
std::cin >> m1 >> m2;

As std::istringstream is derived from std::istream , this operator will work for it as well as all other input stream types.

Answer 2

I'd consider writing an update method that takes a stream instead of using the operator. The flaw with using the operator << is, as you stated, that it's not usually used for that purpose, which will probably irritate everyone looking at your code that doesn't know how you implemented the operator. stream >> model is more commonly used, as stated in the comments.