cpp- static member and function

Question

I have the following student class with two similar function- One is static and one is not.

class Student { public: Student(std::string name_ , int const id_); virtual ~Student(); void addGrade(int const grade2add);//grade above 100 void removeGrade (int const grade2remove); //update maxGrade void print(); //id, name, grades int getStudentMaxGrade(); static int getMaxGrade(); private: std::string name; //max 20 chars int const id; //5 digits, only digits std::vector<int> grades; float avg; static int maxGrade; };

The static int maxGradeis initialize with 0.

I implement the function:

int Student::maxGrade = 0; int Student::getStudentMaxGrade() { return *max_element(grades.begin(), grades.end()); }

I'm not sure how to implement the static function. I tried:

int Student::getMaxGrade() { maxGrade= *max_element(grades.begin(), grades.end()); return maxGrade; }

But it doesn't work (doesn't compile)

I'm not sure how to implement the ststic function That rather depends on what you want it to do, which was never adequately explained. Recall that a static member is not tied to a particular object (that's the whole point of static). In other words, it cannot refer to any particular individual student. — Igor Tandetnik
– Igor Tandetnik, Commented Mar 30, 2016 at 14:03
@Igor, you mean that it is not tied to a particular instance of an object. It is tied to a particular object, namely Student. — Chiel
– Chiel, Commented Mar 30, 2016 at 14:13
@Chiel Student is a class, not an object. If you have Student s;, s is an object; Student isn't. — Igor Tandetnik
– Igor Tandetnik, Commented Mar 30, 2016 at 14:17
@Chiel For most of us an object is an instance of a class "and as such, is a location in memory having a value and possibly referenced by an identifier.". — zdf
– zdf, Commented Mar 30, 2016 at 14:20
FYI if it does not compile you should include the compiler error(s). — NathanOliver
– NathanOliver, Commented Mar 30, 2016 at 14:21

acwaters · Accepted Answer · 2016-03-31 06:07:25Z

The way you have your data laid out, each student knows nothing about the grades of the other students, and the class knows nothing about the grades of any particular student. This is good encapsulation, but in order to retrieve the maximum grade of all students, you have to include a bit of logic to keep track of the maximum grade that has been input. Something like this:

void Student::addGrade (int const grade) { // do the stuff, add the grade if (grade > maxGrade) // Check if the grade is higher than the previous maxGrade = grade; // highest recorded grade and, if so, overwrite it. }

This way, every time a higher grade is input, it becomes the new highest grade, and in that way the class always knows the highest grade without having to keep track of each and every student's grades.

How about removeGrade? @sara8 If what you need is class' maxGrade, you need a different design. Consider adding students in a different class that holds a container of students.

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