Redux Reducer：通过键不变地更新数组中的对象

Question

Question: Update the object in devData array with key = 1 this way: -> update data and dateTime

//Redux state:
{
    info: {
        success: true,
        devData: [
            {
                key: 1,
                data: {            <- update this
                    power: 48 ,
                    unit: "kWh"
                },
                dateTime: "2019-08-24T18:21:21.000Z"  <- update this
            },
            {
                key: 2,
                data: {
                    power: 48,
                    unit: "kWh"
                },
                dateTime: "2019-08-24T18:21:01.000Z"
            }
        ]
    }
}

My update method in reducer:

switch (action.type) {
    case 'update':
        return {
            ...state,
            info: {
                ...state.info,
                devData: state.info.devData.map(currentValue => {
                    if (currentValue.key === 1) {
                        currentValue.data = action.payload.data;
                        currentValue.dateTime = action.payload.dateTime;
                    }
                    return currentValue;
                })
            }
        };
}

My problems:

1. My update method is complicating and ugly, difficult to understand

2. I am not sure, if I am really doing this update in an immutable way

3. I think my update method is computationally expensive , not efficient

I need a method for updating to address the problems above.

Answer 1

First install the immer .

and just update a part of your state which you want.

import produce from "immer"


(...)


switch (action.type) {
  case 'update':
    return produce(state, draft => {
      draft.info.devData[0].data = action.payload.data;
      draft.info.devData[0].dateTime = action.payload.dateTime;
      //This code is working ONLY with devData[0]
      //So, You SHOULD change this above code to work as dynamically.
    });

}

immer is a super simple way to update the state with immutability.

I strongly recommend using it.

Answer 2

case “update”:
const index = this.state.devData.findIndex(v => v.key === 1);

return {
        ...state,
        info: {
            ...state.info,
            devData: 
             [
               return [
       ...state.info.devData.slice(0, index),
       {
          data: action.payload.data,
          dateTime: action.payload.dateTime
       },
       ...state.slice(index + 1)
    ]
             ]
        }
    };

the idea is to first find an index of an element neede to update. after that use spread operators to create new areay made of: slice of everything before element to be updated + updated element + everything after updated element.

ps. writing from my mobile so didnt test it