[C++] Class 공부 & instantiation (+ Struct)

이거 읽어보는게 빠름

https://boycoding.tistory.com/category/C++%20%EC%9D%B4%EC%95%BC%EA%B8%B0/09.%20%EA%B0%9D%EC%B2%B4%EC%A7%80%ED%96%A5%20%ED%94%84%EB%A1%9C%EA%B7%B8%EB%9E%98%EB%B0%8D

'C++ 이야기/09. 객체지향 프로그래밍' 카테고리의 글 목록

 

 

class 공부 : 
- 아무 말 없이 변수 선언하면 private이라 밖에서 접근 X; 

public 명시 (근데 멤버 변수는 보통 private으로 하고, 접근 함수를 public으로 만들잖아 -> ps할땐 시간 절약 겸 보통 다 public)

 

- 변수 안받는 default constructor 구현한 뒤, vector<클래스>(N); 했더니 내가 원하는대로 자동으로 생성되더라.

 

- 클래스 내부에 멤버 함수 선언만 하고, 밖에다가 따로 정의할 때 :
리턴값 클래스::함수이름(){...}
ex) void Garden::spring() { ... }

+ this로 자기 자신 클래스 지칭 가능하나, 생략하고 써도 됨

 

- 콜론 초기화(:) - c++ 멤버 초기화 리스트(Member Initialize List)

https://caileb.tistory.com/165

class Garden {
private:
    int food; // getFood를 통해서만 접근

public:
    Garden() :food(5) {};
    void spring(); // declaration만, 정의는 바깥에
    int getFood() const {
    	return food;
    } // const member function
};

void Garden::spring() {
    this->food;
    food; // this 생략됨
    ...
}

 

 

Class instantiation에 대해 (막상 한번도 해본 적 없는 것 같아서)

www.cplusplus.com/forum/beginner/166003/

Class instantiation, which is the best w - C++ Forum

class Coord {
public:
    int x, y;
    Coord() :x(0), y(0) {};
    Coord(int _x, int _y) :x(_x), y(_y) {}; // member initializer lists
    Coord operator+ (const Coord& addend) {
        return Coord(x + addend.x, y + addend.y);
    }
    ...
}

ostream& operator<< (ostream& os, const Coord& pt) {
    return os << "{" << pt.x << ", " << pt.y << "}";
}

int main() {
    Coord pt1(1, 2); // 일반 
    Coord* pt2_ptr = new Coord(5, 4); // 동적 할당 (new) - 포인터 반환
    cout << pt1 << "\n" << *pt2_ptr << "\n"; // {1, 2} {5, 4}
    cout << pt1 + *pt2_ptr << "\n"; // {6, 6}
}

 

특히 struct instantiation 헷갈림 

https://stackoverflow.com/questions/5914422/proper-way-to-initialize-c-structs

Proper way to initialize C++ structs

C c = C(); // init using default constructor
C* cptr = new C();

C c; // init using default constructor (like line#1)
C c(1, 2, 3); // init using predefined constructor (just like class)

 

struct vs class는 나의 다른 글 참고

https://goldenriver42.tistory.com/34?category=944792 

 

 

(31Mar22) Q. How do I delete a statically instantiated object (instance of a class)? I don't have a pointer to free/delete...

Car c1(500, 10);
// How to 'delete' c1? Cannot use free/delete since c1 is not a pointer...

https://stackoverflow.com/questions/36192499/how-do-i-manually-delete-an-instance-of-a-class

local variable is stored in the stack memory → cleared when the function ends

You still want to delete the data on the stack memory → use 'memset' to clear memory to 0

* Part where I got confused) Since C doesn't have a garbage collector, would static data just stay on the memory all the time, until the programmer explicitly frees it?
→ this applies only to the dynamic allocation. static allocation is cleared by the program automatically. 

 

 

(28May22) Create(instantiate) an object without name

→ 가능!

routerNumToIPs.push_back(std::vector<in_addr_t>()); // 네떡

https://stackoverflow.com/questions/47223913/create-an-object-without-a-name-in-c

 

---

 

참고) copying an object (Shallow copy vs deep copy) → copy constructor for class

 

https://wikidocs.net/20082

https://www.geeksforgeeks.org/shallow-copy-and-deep-copy-in-c/