[Error] [React] [Redux-Saga] reducer null 반환

Error

Unhandled Rejection (Error): When called with an action of type "CONTACTS_SET", the slice reducer for key "contacts" returned undefined. To ignore an action, you must explicitly return the previous state. If you want this reducer to hold no value, you can return null instead of undefined.

reducer 규칙

• state 값으로 null, undefined 넘겨줄 수 없다.
  • 이전 state을 넘기거나 action에서 받아온 payload등을 넘겨야 함

수정

• error

case contactsType.CONTACTS_SET:
    return action.contacts;

• good

case contactsType.CONTACTS_SET:
   return action.contacts ? action.contacts : state;

참고

• reducer 규칙