使用Diamond of death進行C ++打印

Question

首先讓我解釋一下我的等級：

        Person
       /     \
   Student Employee
       \     /
       Intern

每個類都有自己的output函數，它打印其數據成員，我只需打印一次Person 。 問題是Student和Employee不是抽象類，人們也會創建一個類型的對象，所以我不僅可以在Intern級別調用輸出函數。

正如您將在下面的代碼中看到的那樣，我已經設法解決了這個問題，但我認為這很難看並且不是非常多態的。 我已經創建了一個額外的輸出函數，因此它適用於所有情況。 有沒有更好的方法來實現這一目標？

class Person {
    string name;
    int id;
public:
        virtual void output(ostream& out) {
        out << name << "," << id;
    }
}

學生：

class Student : virtual public Person {
    string major;
    int year;
public:
    virtual void output(ostream& out) {
        Person::output(out);
        out << "," << major << "," << year;
    }
    virtual void outputStudOnly(ostream& out) {
        out << "," << major << "," << year;
    }
};

雇員：

class Employee : virtual public Person{
    string jobTitle;
public:
    virtual void output(ostream& out) {
        Person::output(out);
        out << "," << jobTitle;
    }
    virtual void outputEmpOnly(ostream& out) {
        out << "," << jobTitle;
    }
};

實習生：

class Intern : public Student, public Employee {
public:
    virtual void output(ostream& out) {
        Person::output(out);
        Student::outputStudOnly(out);
        Employee::outputEmpOnly(out);
    }
};

Answer 1

那是什么模板方法。 以下是我將如何編寫此代碼：

class Person {
    string name;
    int id;
public:
        void output(ostream& out) {
        out << name << "," << id;
        output_impl(out);
    }
private:
       virtual void output_impl(ostream& ) {}
};

class Student : virtual public Person {
    string major;
    int year;
private:
    virtual void output_impl(ostream& out) {
        out << "," << major << "," << year;
    }

};

class Employee : virtual public Person {
    string jobTitle;
private:
    virtual void output_impl(ostream& out) {
        out << "," << jobTitle;
    }
};

class Intern : public Student, public Employee {
private:
    virtual void output_impl(ostream& out) {
        Student::output_impl(out);
        Employee::output_impl(out);
    }
};

而且你在對象上調用output 。