This article builds upon a previous discussion of state management using Unstated, exploring Unstated-Next, its successor. Unstated-Next leverages React Hooks and the Context API for streamlined state management, offering a more efficient approach than its predecessor, especially given the advancements in React Hooks. We'll examine single and multi-component state management using Unstated-Next. Familiarity with the previous Unstated article is helpful but not strictly required.

Minimal Form Component Example

We'll create a simple React form with a text input for a name and a submit button. Upon submission, the name will be displayed above the form. The complete code is available on GitHub. This example utilizes Create React App and Bootstrap.

First, set up the project:

npx create-react-app unstated-next-form
cd unstated-next-form

Install Unstated-Next:

# yarn
yarn add unstated-next

# npm
npm install --save unstated-next

Import necessary modules into App.js:

// src/App.js
import React, { useState } from 'react';
import { createContainer } from "unstated-next";

Create a custom hook:

// src/App.js
// ...previous imports

const useForm = () => {
  const [input, setValue] = useState("");
  const [name, setName] = useState("Barney Stinson");

  const handleInput = (event) => setValue(event.target.value);
  const updateName = (event) => {
    event.preventDefault();
    setName(input);
    setValue("");
  };

  return { input, name, handleInput, updateName };
};

Create a container using createContainer:

// src/App.js
// ...previous code

const FormContainer = createContainer(useForm);

Create the Form component:

// src/App.js
// ...previous code

const Form = () => {
  const form = FormContainer.useContainer();
  return (
    <div>
      <p>Hello! {form.name}</p>
      <form onsubmit="{form.updateName}">
        <input type="text" value="{form.input}" onchange="{form.handleInput}">
        <button type="submit">Save</button>
      </form>
    </div>
  );
};

Wrap the Form component with the provider in the App component:

const App = () => (
  <formcontainer.provider>
    <form></form>
  </formcontainer.provider>
);

This completes the minimal form example. Try building a simple to-do application using these concepts. A reference repository is available.

Sharing State Across Multiple Components

This example demonstrates sharing state between a form and a to-do list. The user's name, updated in the form, will reflect in the to-do list.

Create a new project and install dependencies:

npx create-react-app unstated-next-app
cd unstated-next-app
yarn add unstated-next shortid

Create store.js to manage shared state:

// src/store.js
import { useState } from "react";
import shortid from "shortid";
import { createContainer } from 'unstated-next';

const useStore = () => {
  const [input, setValue] = useState("");
  const [name, setName] = useState("Barney Stinson");
  const [todos, setTodos] = useState([{ id: 1, title: 'Write code' }, { id: 2, title: 'Buy milk' }]);
  const [item, setItem] = useState("");

  const handleInput = (event) => setValue(event.target.value);
  const updateName = (event) => {
    event.preventDefault();
    setName(input);
    setValue("");
  };
  const handleItem = (event) => setItem(event.target.value);
  const handleSubmit = (event) => {
    event.preventDefault();
    setTodos([...todos, { id: shortid.generate(), title: item }]);
    setItem("");
  };

  return { input, name, handleInput, updateName, todos, item, handleItem, handleSubmit };
};

export const StoreContainer = createContainer(useStore);

Create form.js:

// src/form.js
import React from "react";
import { StoreContainer } from "./store";

const FormComponent = () => {
  const form = StoreContainer.useContainer();
  return (
    <div>
      <p>Hello! {form.name}</p>
      <form onsubmit="{form.updateName}">
        <input type="text" value="{form.input}" onchange="{form.handleInput}">
        <button type="submit">Change Name</button>
      </form>
    </div>
  );
};

export default FormComponent;

Create todo.js:

// src/todo.js
import React from "react";
import { StoreContainer } from "./store";

const TodoComponent = () => {
  const todo = StoreContainer.useContainer();
  return (
    <div>
      <p>Add Todos</p>
      <form onsubmit="{todo.handleSubmit}">
        <input type="text" value="{todo.item}" onchange="{todo.handleItem}">
        <button type="submit">Add</button>
      </form>
      <p>Dear {todo.name}, here are your current tasks:</p>
      <ul>
        {todo.todos.map((item) => <li key="{item.id}">{item.title}</li>)}
      </ul>
    </div>
  );
};

export default TodoComponent;

Update App.js:

import React from 'react';
import TodoComponent from "./todo";
import FormComponent from "./form";
import { StoreContainer } from "./store";

function App() {
  return (
    <storecontainer.provider>
      <formcomponent></formcomponent>
      <todocomponent></todocomponent>
    </storecontainer.provider>
  );
}

export default App;

This revised example provides a more complete and functional illustration of state sharing across multiple components using Unstated-Next. Remember to handle potential errors and edge cases in a production environment.

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