将项目添加到 Reducer 中的空数组中会给出错误“类型错误：传播不可迭代实例的尝试无效”。

Question

I'm tried to declare any empty array in reducer and trying to add some objects in it dynamically.But I got this error when i try to add new item in it.'TypeError: Invalid attempt to spread non-iterable instance.'It means that you don't have any array in which you are trying to add new item?.How's it possible.Here is my reducer state.

const initialState = {
  
  recentSearches: [],
 
};

here is my function firing up

const handleItem = async (item) => {
    let recent = [...recentSearches];
    recent.push(item);
    new Promise((rsl, rej) => {
      addSearchItem(recent, rsl, rej);
    })
      .then((res) => {
        navigation.navigate('SearchDetail', {text: item.name});

        // console.log('Zaid ----->', res);
      })
      .catch((res) => {
        console.log(res);
      });
  };

here is the action to reducer

export const addSearchItem = (data, rsl, rej) => {
  return (dispatch) => {
    try {
      dispatch({
        type: ADD_SEARCH,
        recentSearches: data,
      });
      rsl();
    } catch (err) {
      rej();
    }
  };
};

here is the case

case ADD_SEARCH:
      return {
        ...state,
        recentSearches: action.recentSearches,
      };

Answer 1

you can update an array in redux immutably in this way

return {
...state,
recentSearches:state.recentSearches.concat(item),
}

I hope this will help for more follow this https://redux.js.org/recipes/structuring-reducers/immutable-update-patterns

Answer 2

This error happens when you trying to copy an undefined array in your reducer. eg:

const newList = [...state.someList];

In this case, 'someList' is undefined or not an array. make sure your spelling or you are using the correct array.

Answer 3

尚未修复 上面提供的解决方案