[Recoil] atom, selector

# atom

 

atom은 상태 한개의 단위를 의미한다.

atom을 불러오기 위해서는 useRecoilState라는 훅을 사용한다.

export const wonState = atom({
  key: "wonState",
  default: 0,
});

 

---

 

# selector
- key값을 선언해주고 get이라는 요소가 들어간다.
값을 처리할 함수라고 생각하면 된다. 하지만 무조건 어떤 값을 return 해줘야한다.

-get function을 이용하면 selector 내부에 여러 atom들을 가져올수 있다.

 

export const dollarState = selector({
  key: "dollarState",
  get: ({ get }) => get(wonState) / 1400,
  set: ({ set }, dollar) => set(wonState, dollar * 1400),
});

export const toDoSelector = selector({
  key: "toDoSelector",
  get: ({ get }) => {
    const toDos = get(toDoState);
    return [
       toDos.filter((toDo) => toDo.category === "To_Do"),
       toDos.filter((toDo) => toDo.category === "DOING"),
       toDos.filter((toDo) => toDo.category === "DONE"),
     ];
   },
});