Brian Neville-O'Neill

Posted on May 20, 2020 • Originally published at blog.logrocket.com on May 1, 2020

State management with Unstated Next

#react

Written by Abdulazeez Abdulazeez Adeshina✏️

State is a foundational part of React applications, which means managing state is hugely important. Since the introduction of the Context API and then Hooks, managing state has been relatively easy since the Context API helps save us the stress of using Redux.

As a result, multiple state management libraries have been published to further facilitate state management with the Context API, and in this article, I’ll be looking into Unstated N ext.

What is Unstated Next?

Unstated Next is a library built on React’s Context API that allows the sharing of state globally in our applications. Unstated Next has simple API methods, which can be used either as Hooks or component methods. In the subsequent sections, I’ll discuss the API methods and then build a simple demo to demonstrate how Unstated Next works.

Unstated Next can be installed from either Yarn or npm:

yarn add unstated-next 

// or

npm install unstated-next

What problems does Unstated Next solve ?

Since Unstated Next is built on the Context API, it solves the same problems that the Context API solves. Unstated Next allows us to:

Access parent state from child components
Avoid prop drilling

If you are not familiar with the Context API, it is advisable to read this article before proceeding.

Unstated Next API methods

Unstated Next houses three API methods, and I’ll discuss each one briefly:

`createContainer(ourHook)`

The createContainer method is used to initialize context and takes as an argument the Hook whose state is to be shared globally. This context is traditionally assigned to a variable, as shown below:

import { createContainer } from 'unstated-next'

function ourHook() {}

let ourContext = createContainer(ourHook)
// ourContext == {Provider, useContainer}

The variable, in turn, returns a provider and useContainer method. The useContainer method can also be referred to as the consumer.

Provider method

The provider method, which is appended to the context, takes in an optional initial value to be rendered on the application’s first render and accepts a child component to be rendered. Here’s an example of its usage:

import { createContainer } from 'unstated-next'

...

function Component() {}

<OurContainer>
  <Component />
</Ourcontainer>

<OurContainer initialState={"initial value"} />
  <Component />
</Ourcontainer>

`useContainer(ctx)`

The useContainer(ctx) Hook takes in the context variable as an argument and is stored in a variable that will be used to access the global state. The useContainer(ctx) Hook is used in the component where state is to be accessed — in this case, the child component. This will be demonstrated in the next section.

import { useContainer } from "unstated-next"

function ChildComponent() {
  let activity = useContainer(OurContainer)
  return <input value={activity.value} onChange={activity.onChange} />
}

The above are the available API methods in the Unstated Next libraries, which are purely built on the React API. In the next section, I’ll be building a simple to-do app to demonstrate how the methods work.

Setup

Before we dive in too deep, let’s map out the project structure and the installation of the dependencies needed for our to-do app. We’ll start by creating our project folder.

mkdir unstated-todo-app && cd unstated-todo-app
mkdir public src src/components
cd public && touch index.html style.css
cd ../src && touch index.js
cd components && touch Todos.js

Next, we’ll initialize the directory and install the dependencies needed.

npm init -y
npm i react react-dom react-scripts unstated-next

Now it’s time to write the App rendering component in the index.js file.

`index.js`

This file houses the component responsible for rendering our Todos component. First, I’ll import the dependencies needed:

import React from "react";
import { render } from "react-dom";
import TodoList from "./Components/Todos";

Don’t fret, the TodoList component will be built after this. Next, we tell React to render our app on the div node with an identifier "root":

function App() {
  return (
    <>
      <h3> Unstated Todo App </h3>
      <hr />
      <TodoList />
    </>
  )
}

render(<App />, document.getElementById("root"))

Next, we’ll begin writing the Todos component.

`Todos.js`

The Todos component comprises a custom Hook which will be handling the state for our to-do app alongside some state methods and a component that lets us add and renders our to-do.

We’ll start off by creating our custom hook and initializing with two state objects:

import React, { useState } from "react";

function useTodos(initialstate = [{todo: "Test todo"}]) {
  let [todos, setTodo] = useState(initialstate)
  let [todo, setTodoItem] = useState("")

Our Hook useTodos() takes an initial to-do (which is optional) that is rendered when the app is loaded. It has two state objects: todos and todo. The todos state object is an array of all the to-dos in our app, while the todo state object is the to-do added to the todos array and has an initial value of an empty string.

The todo is set from the user input and then added to the todos array by means of a setTodo() method, which we’ll be looking at next.

  ...
  const handleInput = e => {
    setTodoItem(e.target.value)
  }

  const addTodo = e => {
    e.preventDefault()
    setTodo([...todos, {todo}])
    setTodoItem("")
  }

  const removeTodo = id => {
    const todoList = todos.filter(todo => todo.todo !== id)
    return setTodo(todoList)
  }

  return { todos, todo, addTodo, removeTodo, handleInput }

}

The handleInput() method is used to set the todo state to the value the user inputs in the form by using the setTodoItem state handler.
The addTodo() method adds the to-do item into the todos array by means of the setTodo([...todos, todo]) method. It then sets the todo state to an empty string.
The removeTodo() method removes a to-do from the todos array.

Then, we return the values of the state and the Hook’s method so it can be accessible in our components.

Next, we’ll create a container from our useTodo() Hook. First, we’ll import the createContainer Hook from Unstated Next:

// After the react import
import { createContainer } from "unstated-next";

Then we create the container that will be used in our components. It gives us direct access to our app’s state and its method, as discussed in the previous section:

let Todos = createContainer(useTodos)

The container doesn’t do anything yet, and we haven’t built the components for the to-do. You guessed right — we’ll be building that next.

function Todo({ todo }) {
  let todosContainer = Todos.useContainer()
  return (
    <>     
      <ul className="w3-ul w3-card-4">
        <li key={todo.todo} className="w3-display-container" >
           {todo.todo}
           <span className="w3-button w3-transparent w3-display-right" onClick={() => todosContainer.removeTodo(todo.todo)}>&times;</span>
        </li>
      </ul>
    </>
  )
}

The component above is responsible for rendering the todo passed as a prop from an iteration of the todos array.

Next, we build the consumer component that displays the to-dos and let us add a to-do:

function DisplayTodos() {  
  let todosContainer = Todos.useContainer()
  return (
    <React.Fragment>
      <input type="text" className="w3-input w3-border w3-round" placeholder="Write an article" value={todosContainer.todo} onChange={todosContainer.handleInput} />
      <button onClick={todosContainer.addTodo} className="w3-button w3-round w3-black">Add Todo</button>
      <hr />
      {
        todosContainer.todos.map(todo => (
          <Todo todo={todo} />
        ))
      }
    </React.Fragment>
  )
}

On lines 8–12, we iterate over the todos array state and then pass each todo as a prop to the Todo component.

In the components above, the container is used from the variable todosContainer to allow access to the states and its methods, as can be seen in the render blocks of each component.

Next, we define a component that renders the consumer component DisplayTodos() under the context provider since nothing can be consumed without a provider.🙂

export default function TodoList() {
  return (
    <Todos.Provider>
      <DisplayTodos />
    </Todos.Provider>
  )
}

We make the component a default export since it has been imported to be rendered in the App component.

Running our app

With the completion of our app’s build process, we are yet to write the code for the index.html and style.css files. Let’s do that before we proceed:

`index.html`

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <link rel="stylesheet" href="https://www.w3schools.com/w3css/4/w3.css">
  <link rel="stylesheet" href="style.css" type="text/css">
  <title>Unstated-next Recipe App</title>
</head>
<body>
  <div id="root" class="w3-container"></div>
</body>
</html>

`style.css`

body {
  font-family: 'Gill Sans', 'Gill Sans MT', Calibri, 'Trebuchet MS', sans-serif;
  background-color: antiquewhite;
}

After that, let’s configure package.json so we can run our app. Under the scripts section, replace the code there with:

"start": "react-scripts start"

With that done, let’s start the app and view it live on http://localhost:3000:

npm run start

Here’s a demonstration of the app in use:

Conclusion

This article should give you a basic understanding of what Unstated Next is, its features, and how it works. The main takeaway is that you can use Unstated Next in place of the traditional React Context API Hooks and Redux.

Unstated Next is an excellent React library for managing state apps. However, be aware that there are cases in which the Context API, and thus Unstated Next, shouldn’t be used. Read about them in this article. The code used in this article can be found on GitHub.

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