打印出向量中的输入，并将 function 包含在 main 中。 c++

Question

Anyone got any tips for me? I need to print out the vector, but i cant get the function included into main. The relevant part is the "void print" and "print(klasse)" in main. The criteria for the assignment is:

1. Asks for the name of a student

2. asks for the name of a course and the grade the student got

3. Does this until course name is "stop"

4. Then asks for a new student until the name is "stop"

5. Then prints out the grades gathered for each student

    #include <iostream> #include <string> #include <vector> #include <list> #include <algorithm> #include <iterator> using namespace std; class student_i { public: string name; string course; string grade; }; void print(std::vector<student_i> const &klasse) { std::copy(klasse.begin(), klasse.end(), std::ostream_iterator<int>(std::cout, " ")); } int main() { student_i klasse; std::vector<student_i> studenter; for (int i = 0; i < 64; i++) { std::cout << "Enter student name: " << std::endl; getline(std::cin, klasse.name); studenter.push_back(klasse); if ( klasse.name == "stop") { //Why doesnt this function work in main? print(klasse); return 0; } for (int i = 0; i < 64; i++) { std::cout << "Enter student course: " << std::endl; getline(std::cin, klasse.course); if (klasse.course == "stop") { break; } std::cout << "Enter student grade: " << std::endl; getline(std::cin, klasse.grade); } } return 0;

   }

Answer 1

Your issue here is that you ask to "copy" your std::vector<student_i>::iterator into a std::ostream_iterator<int> instead of an std::ostream_iterator<student_i> (which are very much not the same). You should change that.

However the compiler will complain that you then need to define the operator<< on the type student_i . Here is how I would do it (you should get familiar with this definition of operator<<, it is encountered quite frequently):

std::ostream& operator<<(std::ostream& stream, const student_i& stud) {
  stream << stud.name << " " << stud.course << " " << std.grad;
  return stream;
}

Quick note: you made all your attributes public in the class student_i so this will work fine, but this is often not the case (attributes are generally private). In such case, it is common practice to declare the operator<< friend to the class, so you can still access the attributes in its body:

class student_i {
  friend std::ostream& operator<<(std::ostream&, const student_i&);
  private:
    std::string name; 
    ...
      

You can now write something like

student_i student;
student.name = "danlon"; 
student.course = "CS"; 
student.grad = "A";
std::cout << student << std::endl;

Once this function is defined, I think your print function should work.