**Solved it, thanks!** - For anyone interested, I was trying to access state.tasks.data within the reducer however due to scope, I could access it via state.data as I was already within the tasks slice.

---

**Edit:** My issue with mutated state error is now fixed, it was due to sorting the state directly without creating a new array from it. That has been fixed with `concat()` before `sort()`.

My new issue is that `state` within my `removeTask reducer` is no longer accessible. It's now returning undefined. If I `console.log(state)` then it will return a `Proxy` with:

```
[[Handler]]: null,
[[Target]]: null,
[[IsRevoked]]:true

```

**Edit 2:** I've found that the Proxy is due to `immer` under the hood which does something with the mutation to use it in a way that the `state` is not mutated. I've still yet to fix the issue of `state.tasks.data` returning `undefined`.

---

I'm using react-redux and redux-toolkit. I am just learning Redux so my head is fried, haven't a clue.

I've followed some information from the redux-toolkit basic tutorial on their website which says that you can mutate state in the reducers because toolkit does something behind the scenes to stop it actually mutating the state:

<https://redux-toolkit.js.org/tutorials/basic-tutorial>

In any case, the counter example they provide mutates the state. The increment reducer returns `state += 1` - this works fine

Now I've got my own thing going where I have the `initial state` set to an array of objects I've pulled in. See below:

`tasksSlice.js`:

```
import { createSlice } from "@reduxjs/toolkit";
import data from "data/tasks_data.json";

export const tasksSlice = createSlice({
  name: "tasks",
  initialState: {
    data: data,
  },
  reducers: {
    removeTask: (state, action) => {
      const { id } = action.payload;
      const { data } = state.tasks;
      data = data.filter((item) => id !== item.id);
    },
  },
});

export const { removeTask } = tasksSlice.actions;

export const selectTasks = (state) => state.tasks.data;

export default tasksSlice.reducer;

```

Now I've got the tasks listed out in my `tasks` component. Each task is listed using a `taskItem` component. Inside the `taskItem` component I have a delete button which I have set the `onClick` event to use the `removeTask` reducer.

```
<button
  className={`${styles.task_button} ${styles.delete}`}
  onClick={() => dispatch(removeTask(id))}
>
  <MdDeleteForever />
</button>

```

This is passing the "customer\_id" field from the `data` that's mapped out into the task list from `initial state`.

I want to be able to delete the task so I'm trying to mutate it (as toolkit said I can) by filtering the `state.tasks.data` and returning everything apart from the task where the `id` is a match.

Unfortunately I keep getting an error message:

`Error: Invariant failed: A state mutation was detected between dispatches, in the path 'tasks.data.0'. This may cause incorrect behavior.`

---

`tasks.js` - Tasks container component (quite messy):

```
import React, { useState, useEffect } from "react";
import SectionHeading from "components/SectionHeading/SectionHeading";
import { useSelector } from "react-redux";
import { selectTasks } from "redux/tasks/tasksSlice";
import TaskSelect from "./TaskSelect";
import TaskTabs from "./TaskTabs";
import TaskItem from "./TaskItem";
import styles from "./Tasks.module.scss";
// import tasks_data from "data/tasks_data.json";

const Tasks = () => {
  const tasksData = useSelector(selectTasks);
  console.log(tasksData);
  const [taskTab, setTaskTab] = useState({ activeTask: "All" });
  const [size, setSize] = useState({ width: 65, left: 0 });
  // const [tasksData, setTasksData] = useState(tasks_data);

  const taskTypes = [
    "All",
    "Quotes",
    "Domains",
    "SSL Setup",
    "SEO Setup",
    "Other",
  ];

  useEffect(() => {
    const activeBar = document.querySelector(".active_bar");
    const active = document.querySelector(".active_btn");
    if (size) {
      activeBar.style.width = `${active.offsetWidth}px`;
      activeBar.style.transform = `translate(${active.offsetLeft}px, ${active.offsetTop}px)`;
    }
  });

  const setActive = (e, type) => {
    setTaskTab({ activeTask: type });
    setSize(false);
    const activeBar = document.querySelector(".active_bar");
    activeBar.style.width = `${e.target.offsetWidth}px`;
    activeBar.style.transform = `translate(${e.target.offsetLeft}px, ${e.target.offsetTop}px)`;
  };

  const changeActive = (e) => {
    setTaskTab({ activeTask: e.target.value });
  };

  const getDaysDue = (days) => {
    const { days_due, overdue } = days;
    if (overdue === true) {
      if (days_due === -1) {
        return `${Math.abs(days_due)} day overdue`;
      } else {
        return `${Math.abs(days_due)} days overdue`;
      }
    } else if (days_due === 0) {
      return "Today";
    } else if (days_due === 1) {
      return `${days_due} day`;
    } else if (days_due > 1) {
      return `${days_due} days`;
    } else {
      return "Error getting days due";
    }
  };
  return (
    <article className="tasks">
      <TaskTabs
        taskTypes={taskTypes}
        click={setActive}
        activeTask={taskTab.activeTask}
        data={tasksData}
      />
      <TaskSelect taskTypes={taskTypes} change={changeActive} />
      <SectionHeading>Tasks: {taskTab.activeTask}</SectionHeading>
      <section className={styles.tasks_list}>
        {tasksData
          .sort((a, b) => a.days.days_due - b.days.days_due)
          .filter((task) =>
            taskTab.activeTask === "All"
              ? true
              : task.type === taskTab.activeTask
          )
          .map(
            ({
              customer_id,
              account_name,
              days,
              days: { days_due, overdue },
              type,
            }) => {
              return (
                <TaskItem
                  key={customer_id}
                  id={customer_id}
                  name={account_name}
                  days={getDaysDue(days)}
                  overdue={overdue}
                  daysDue={days_due}
                  type={type}
                />
              );
            }
          )}
      </section>
    </article>
  );
};

export default Tasks;

```

---

`TaskItem.js`:

```
import React from "react";
import { useDispatch } from "react-redux";
import { removeTask } from "redux/tasks/tasksSlice";
import { Link } from "react-router-dom";
import { MdModeEdit, MdDeleteForever } from "react-icons/md";
import styles from "./TaskItem.module.scss";

const TaskItem = ({ id, name, days, daysDue, overdue, type }) => {
  const dispatch = useDispatch();
  return (
    <article
      className={`
    ${styles.task} 
    ${daysDue === 0 ? `${styles.today}` : ""} 
    ${overdue === true ? `${styles.overdue}` : ""}
    `}
    >
      <Link to="/" className={styles.task_name}>
        {name}
      </Link>

      <span
        className={`${styles.task_days} ${
          daysDue === 0 ? `${styles.task_days__today}` : ""
        } ${overdue ? `${styles.task_days__overdue}` : ""}`}
      >
        <strong>{type}</strong>: {days}
      </span>

      <div className={styles.task_buttons}>
        <button className={`${styles.task_button} ${styles.edit}`}>
          <MdModeEdit />
        </button>

        <button
          className={`${styles.task_button} ${styles.delete}`}
          onClick={() => dispatch(removeTask(id))}
        >
          <MdDeleteForever />
        </button>
      </div>
    </article>
  );
};
export default TaskItem;

```

`tasks_data.json`:

```
[
  {
    "account_name": "Misty's Gym",
    "customer_id": 1,
    "days": {
      "days_due": 1,
      "overdue": false
    },
    "type": "Quotes"
  },
  {
    "account_name": "Brock's Diner",
    "customer_id": 2,
    "days": {
      "days_due": 0,
      "overdue": false
    },
    "type": "Quotes"
  },
  {
    "account_name": "Samurai Champloo's Fish Bar",
    "customer_id": 3,
    "days": {
      "days_due": 5,
      "overdue": false
    },
    "type": "SSL Setup"
  },
  {
    "account_name": "Tiny Rebel",
    "customer_id": 4,
    "days": {
      "days_due": -7,
      "overdue": true
    },
    "type": "Domains"
  },
  {
    "account_name": "Matalan",
    "customer_id": 5,
    "days": {
      "days_due": 13,
      "overdue": false
    },
    "type": "Other"
  },
  {
    "account_name": "Lowes Soft Drinks",
    "customer_id": 6,
    "days": {
      "days_due": 1,
      "overdue": false
    },
    "type": "SEO Setup"
  },
  {
    "account_name": "Snack 'n' Go",
    "customer_id": 7,
    "days": {
      "days_due": -2,
      "overdue": true
    },
    "type": "Quotes"
  },
  {
    "account_name": "Jeronemo",
    "customer_id": 8,
    "days": {
      "days_due": 5,
      "overdue": false
    },
    "type": "Quotes"
  },
  {
    "account_name": "Tom's Mouse Traps",
    "customer_id": 9,
    "days": {
      "days_due": 0,
      "overdue": false
    },
    "type": "Domains"
  },
  {
    "account_name": "Contiente",
    "customer_id": 10,
    "days": {
      "days_due": 2,
      "overdue": false
    },
    "type": "Domains"
  },
  {
    "account_name": "Um Bongo",
    "customer_id": 11,
    "days": {
      "days_due": -1,
      "overdue": true
    },
    "type": "SEO Setup"
  }
]

```

What on earth am I doing wrong? How else can I set the state?

Cheers.