I'm used to oveerriding the Java toString() method on my own objects in classes, but I'm not sure where I'm going wrong with the following code:
struct Student { std::string name; int age; double finalGrade; std::string toString() { return "Name: " + name + "\n Age: " + age + "\n Final Grade: " + finalGrade; }
};I'm only beginning to learn c++ so any advice would be appreciated
64 Answers
In contrast to java, C++ does not offer a predefined "toString"-method that is called implicitly whenever a string representation of an object is requested. So your toString-method will have to be called explicitly then.
In C++, however, something similar is available by overriding the operator << for streams. Thereby, you can directly "send" the object contents to a stream (without the need to store everything in an intermediate string object). And you can use the same code to populate a string to be returned by a toStringmethod, too:
struct Student { std::string name; int age; double finalGrade; std::string toString() const;
};
ostream& operator << (ostream &os, const Student &s) { return (os << "Name: " << s.name << "\n Age: " << s.age << "\n Final Grade: " << s.finalGrade << std::endl);
}
std::string Student::toString() const { stringstream ss; ss << (*this); return ss.str();
}
int main() { Student stud { "john baker", 25, 1.2 }; std::cout << "stud directly: " << stud << endl; std::string studStr = stud.toString(); std::cout << "stud toString:" << studStr << endl;
}You can't add anything you want to a std::string like you can to a Java String. Notably, most objects are not expected to have a toString member function. However, the standard library provides std::to_string which allow you to convert numeric values to an std::string. For example you could wrap the numeric values with a std::to_string to fix your function :
#include <string>
struct Student { std::string name; int age; double finalGrade; std::string toString() { return "Name: " + name + "\n Age: " + std::to_string(age) + "\n Final Grade: " + std::to_string(finalGrade); }
};Edit : Though this answer explains why what you tried doesn't work, the other answer's solution is the preferred approach.
0You cant add int to std::string because the std::string operator+ was not overloaded to int.
The best solution is to use string stream :
#include <sstream>
std::string toString() { std::ostringstream strout; strout<< "Name: " << name << "\n Age: " << age << "\n Final Grade: " << finalGrade; return strout.str();
}You cannot just add an int or a double to an std::string. Use std::to_string to convert them first. This should work fine:
std::string toString() { return "Name: " + name + "\n Age: " + std::to_string(age) + "\n Final Grade: " + std::to_string(finalGrade); }
