C++用死亡之钻印刷

C++ printing with Diamond of death

本文关键字：C++ 更新时间：2023-10-16

首先让我解释一下我的层次结构：

Person
/     
Student Employee
     /
Intern

每个类都有自己的output函数，它打印它们的数据成员，我只需要打印一次Person。问题是Student和Employee不是抽象类，人们也会做自己类型的对象，所以我不能只在Intern级别调用输出函数。

正如您将在下面的代码中看到的那样，我已经设法解决了这个问题，但我认为这很丑陋并且不是很多态 .我创建了一个额外的输出函数，因此它适用于所有情况。有没有更好的方法来实现这一目标？

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

学生：

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;
}
};

员工：

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;
}
};

和实习生：

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

模板方法的用途。以下是我编写此代码的方式：

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);
}
};

而不是你在对象上调用output。

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