State management is at the core of any React application, and for more complex scenarios, the useReducer hook provides a powerful way to manage state in a structured manner. In this article, we'll explore useReducer through a concrete example: creating a to-do list.

Understanding useReducer

useReducer is a React hook that allows state management using a reducer pattern. Instead of using useState to manage a component's state, useReducer is particularly suitable for handling complex states, such as lists of data.

The basic idea is to provide a reducer function that takes two arguments: the current state and the action to perform.

• The action is typically an object that describes a change in state, such as adding a task, deleting it, or marking it as done.
• The reducer function returns the new state based on the current state and the action.

Pratical exemple : Creating a To-Do List with useReducer

Imagine you're developing a to-do list application. Here's how you can use useReducer to manage the list of tasks:

import React, { useReducer } from 'react';

// Define a reducer function
const taskReducer = (state, action) => {
  switch (action.type) {
    case 'ADD_TASK':
      return [...state, { id: Date.now(), text: action.text, done: false }];
    case 'DELETE_TASK':
      return state.filter(task => task.id !== action.id);
    case 'TOGGLE_TASK':
      return state.map(task =>
        task.id === action.id ? { ...task, done: !task.done } : task
      );
    default:
      return state;
  }
};

function TaskList() {
  // Replace useState by useReducer with reducer and initial state
  const [tasks, dispatch] = useReducer(taskReducer, []);

  // make tasks for the reducer
  const addTask = text => {
    dispatch({ type: 'ADD_TASK', text });
  };

  const deleteTask = id => {
    dispatch({ type: 'DELETE_TASK', id });
  };

  const toggleTask = id => {
    dispatch({ type: 'TOGGLE_TASK', id });
  };

  return (
    <div>
      <h1>To-Do List</h1>
      <ul>
        {tasks.map(task => (
          <li key={task.id}>
            <span
              style={{ textDecoration: task.done ? 'line-through' : 'none' }}
            >
              {task.text}
            </span>
            <button onClick={() => toggleTask(task.id)}>
              {task.done ? 'Undo' : 'Done'}
            </button>
            <button onClick={() => deleteTask(task.id)}>Delete</button>
          </li>
        ))}
      </ul>
      <input
        type="text"
        placeholder="Add a task"
        onKeyUp={e => {
          if (e.key === 'Enter' && e.target.value) {
            addTask(e.target.value);
            e.target.value = '';
          }
        }}
      />
    </div>
  );
}

In this example, we've created a to-do list application. We use useReducer to manage the tasks. Actions like ADD_TASK, DELETE_TASK, and TOGGLE_TASK allow us to modify the state of the task list in a structured way.

Benefits of useReducer for Task Management

useReducer brings several advantages for managing a to-do list in a React application:

• Structure and Readability: Actions are explicitly defined with types, making the code more readable and maintainable.

• Immutable State: useReducer encourages state immutability, which avoids side effects and unexpected errors.

• Handling Complex States: useReducer is ideal for managing a list of data with many possible actions.

• Separation of Concerns: By grouping actions and reduction logic in a single function, useReducer promotes the separation of concerns.

• Potential for Future Extensions: You can easily add new actions to extend your application's functionality.

Conclusion

In conclusion, useReducer is a powerful tool for managing the state of a React application, especially when dealing with complex states and a variety of possible actions.
By incorporating it into your projects, you can create more robust and structured applications while improving code maintainability and readability.