C++ 집합 관계 (Aggregation Relationship)

집합 관계 (Aggregation Relationship)

• 교사 클래스와 학생 클래스로 비유

구성 관계로 작성했을 경우

• 각 Lecture의 Student 멤버는 서로 다른 메모리 공간을 차지하여 공유되지 않는다.

  main.cpp

  #include "Lecture.h"
  
  int        main()
  {
    using namespace std;
  
    Teacher t1("Prof. Hong");
    Teacher t2("Prof. Good");
    Student s1("Jack Jack", 0);
    Student s2("Dash", 1);
    Student s3("Violet", 2);
  
    Lecture lec1("Introduction to Computer Programming");
    lec1.assignTeacher(t1);
    lec1.registerStudent(s1);
    lec1.registerStudent(s2);
    lec1.registerStudent(s3);
  
    Lecture lec2("Computational Thinking");
    lec2.assignTeacher(t2);
    lec2.registerStudent(s1);
  
    cout << lec1 << endl;
    cout << lec2 << endl;
  
    lec2.study();
  
    cout << lec1 << endl;
    cout << lec2 << endl;
  }
  
  /* stdout
  --- Introduction to Computer Programming ---
  Teacher
                  Prof. Hong
  Students
                  Jack Jack 0
                  Dash 1
                  Violet 2
  
  --- Computational Thinking ---
  Teacher
                  Prof. Good
  Students
                  Jack Jack 0
  
  << Computational Thinking studied! >>
  
  --- Introduction to Computer Programming ---
  Teacher
                  Prof. Hong
  Students
                  Jack Jack 0
                  Dash 1
                  Violet 2
  
  --- Computational Thinking ---
  Teacher
                  Prof. Good
  Students
                  Jack Jack 1
  */

  Lecture.h

  #pragma once
  
  #include <vector>
  #include "Student.h";
  #include "Teacher.h";
  
  class Lecture
  {
    std::string                name_;
  
    Teacher                    teacher_;
    std::vector<Student>    students_;
  
  public:
    Lecture(const std::string& name_in)
      : name_{name_in}
    {}
  
    void    assignTeacher(const Teacher& const teacher_input)
    {
      teacher_ = teacher_input;
    }
  
    void    registerStudent(const Student& const student_input)
    {
      students_.push_back(student_input);
    }
  
    void    study()
    {
      for (auto& e : students_)
        e.setIntel(e.getIntel() + 1);
      std::cout << "<< " << name_ << " studied! >>\n\n";
    }
  
    friend std::ostream& operator << (std::ostream& out, const Lecture& lecture)
    {
      out << " --- "<< lecture.name_ << " ---\n";
      out << "Teacher\n\t\t" << lecture.teacher_ << '\n';
      out << "Students\n";
      for (auto& e : lecture.students_)
        out << "\t\t" << e << '\n';
      return out;
    }
  };

  Teacher.h

  #pragma once
  
  #include <iostream>
  
  class Teacher
  {
    std::string name_;
  
  public:
    Teacher(const std::string& name_in = "No Name")
      : name_{name_in}
    {}
  
    void    setName(const std::string& name_in)
    {
      name_ = name_in;
    }
  
    std::string    getName()
    {
      return name_;
    }
  
    friend std::ostream& operator << (std::ostream& out, const Teacher& teacher)
    {
      out << teacher.name_;
      return out;
    }
  };

  Student.h

  #pragma once
  
  #include <iostream>
  
  class Student
  {
    std::string name_;
    int            intel_;
  
  public:
    Student(const std::string & name_in = "No Name", const int &intel_in = 0)
      : name_{name_in}, intel_{intel_in}
    {}
  
    void    setName(const std::string& name_in)
    {
      name_ = name_in;
    }
  
    void    setIntel(const int& intel_in)
    {
      intel_ = intel_in;
    }
  
    int        getIntel()
    {
      return intel_;
    }
  
    friend std::ostream& operator << (std::ostream& out, const Student& student)
    {
      out << student.name_ << ' ' << student.intel_;
      return out;
    }
  };

---

집합 관계로 작성했을 경우

• 포인터를 이용하여 main 함수의 인스턴스에 접근하는 것이므로 같은 메모리 공간을 가리킨다.

  main.cpp

  #include "Lecture.h"
  
  int        main()
  {
      using namespace std;
  
      Teacher t1("Prof. Hong");
      Teacher t2("Prof. Good");
      Student s1("Jack Jack", 0);
      Student s2("Dash", 1);
      Student s3("Violet", 2);
  
      Lecture lec1("Introduction to Computer Programming");
      lec1.assignTeacher(&t1);
      lec1.registerStudent(&s1);
      lec1.registerStudent(&s2);
      lec1.registerStudent(&s3);
  
      Lecture lec2("Computational Thinking");
      lec2.assignTeacher(&t2);
      lec2.registerStudent(&s1);
  
      cout << lec1 << endl;
      cout << lec2 << endl;
  
      lec2.study();
  
      cout << lec1 << endl;
      cout << lec2 << endl;
  }
  
  /* stdout
  --- Introduction to Computer Programming ---
  Teacher
                  Prof. Hong
  Students
                  Jack Jack 0
                  Dash 1
                  Violet 2
  
  --- Computational Thinking ---
  Teacher
                  Prof. Good
  Students
                  Jack Jack 0
  
  << Computational Thinking studied! >>
  
  --- Introduction to Computer Programming ---
  Teacher
                  Prof. Hong
  Students
                  Jack Jack 1
                  Dash 1
                  Violet 2
  
  --- Computational Thinking ---
  Teacher
                  Prof. Good
  Students
                  Jack Jack 1
  */

  Lecture.h

  #pragma once
  
  #include <vector>
  #include "Student.h";
  #include "Teacher.h";
  
  class Lecture
  {
    std::string                name_;
  
    Teacher                    *teacher_;
    std::vector<Student *>    students_;
  
  public:
    Lecture(const std::string& name_in)
      : name_{name_in}
    {}
  
    void    assignTeacher(Teacher * const teacher_input)
    {
      teacher_ = teacher_input;
    }
  
    void    registerStudent(Student * const student_input)
    {
      students_.push_back(student_input);
    }
  
    void    study()
    {
      for (auto& e : students_)
        e->setIntel(e->getIntel() + 1);
      std::cout << "<< " << name_ << " studied! >>\n\n";
    }
  
    friend std::ostream& operator << (std::ostream& out, const Lecture& lecture)
    {
      out << " --- "<< lecture.name_ << " ---\n";
      out << "Teacher\n\t\t" << *lecture.teacher_ << '\n';
      out << "Students\n";
      for (auto& e : lecture.students_)
        out << "\t\t" << *e << '\n';
      return out;
    }
  };