React Advanced: Manage Server States in the right way
Tags: webdev, javascript, react, frontend
Published: 2023-09-29 18:54:42

Hello, developer. Today we'll tackle a crucial topic: managing server states in an advanced React app. No frills, just the essential facts on how to make this aspect work efficiently.

### React and its Dirty Work
You know how powerful React is in handling the frontend. But now, let's talk about something more substantial: how does React manage data exchange with the backend? The answer? Server states.

### Connecting the Dots
Server states are the glue that holds together the frontend and backend. Nothing magical, just the need to make these two worlds communicate coherently and without frills.

### Order in Chaos
Centralization is the key. Imagine having a central place where all the data resides. Sounds neat, right? And that's exactly what you want to avoid chaos when things get more complex.

### A Bit of Realism
We're not here to tell you fairy tales. Managing server states can be complicated. It's the practical and sometimes challenging side of development. But no need to panic; we'll face the challenges together.

### Beyond the Basic Concept
We won't stop at defining the basic concept. We want to equip you with tools to go beyond, to tackle complex scenarios, and enhance your application.

So, enough talk. We're here to handle the dirty work and give you the information you need to make server states work smoothly in React. Ready to dive into the details? Let's get to it.

## Role of Server States in a React Application

The effective management of server states forms the backbone of an advanced React application. In this chapter, we will delve into the crucial role that server states play in the React development ecosystem.

### Dynamic Communication
Server states act as a vital bridge between the frontend and backend of an application. They enable dynamic communication, allowing the frontend to efficiently receive and send data to the server. This interaction is essential for real-time and dynamic applications, such as those requiring instant or live updates.

### Centralization of State
A crucial aspect is the centralization of server states. By maintaining a centralized state, the application reduces the chances of inconsistencies and simplifies data management. This approach promotes a clear and organized structure, making code understanding and maintenance more straightforward.

### Managing Complexity
In complex projects, manually handling server states can become a challenge. Utilizing tools like Redux or React's Context API helps simplify this management. These libraries provide a structured way to organize states, facilitating their management and manipulation.

### State Preservation
Once received, server states must be efficiently preserved to ensure a consistent user experience. This may involve caching strategies or local state preservation techniques, thereby reducing the continuous dependency on the server for static data.

### UI Reactivity
Thanks to server states, the user interface can dynamically react to changes in the server-side state. For example, a real-time chat could instantly update messages without requiring a page reload, thereby enhancing the overall user experience.

### Reducing Network Traffic
By maintaining a centralized server state, network traffic can be reduced. Instead of constantly requesting data from the server, the application can optimize requests, reducing loading times and improving overall performance.

In summary, fully understanding and leveraging the role of server states in a React app is crucial for the development of modern and high-performance applications. In the upcoming chapters, we will explore in-depth how to recognize, manage, and address issues arising from poorly managed server states.

## How to Recognize a Server State

Alright, now that we have a good overview of what server states are, it's time to learn how to recognize them when you encounter them in the wild world of React. Don't worry, they're not invisible, just a bit elusive.

### HTTP Request
One of the most obvious ways to understand that you're dealing with a server state is the good old HTTP smoke signal. When you send requests to the server and receive responses, you're looking at server state traffic. It's like the server sending you a message saying, "Hey, I've got something for you!"

### State Manipulation in Effects
Whenever you see a `useEffect` manipulating data reactively, you're probably playing with a server state. It's like React telling you, "Hold on, I need to sync up with the server."

### Outdated States
If you have to update data because it became outdated after a user's change, well, maybe that data is coming from a server.

In essence, recognizing a server state is a bit like learning to read tracks in the desert. There are signs everywhere; you just need to know what to look for. Ready to follow the tracks of server states in your code? Let's track them down!

## Problems Arising from Poor Management

Now that we've learned how to recognize server states, it's time to tackle the less glamorous part of the equation: what happens when things go wrong. Yes, because even server states can cause trouble, especially if they're not handled with the right dose of attention.

### Data Inconsistency
Imagine your server state as a group of musicians playing together. If they're not synchronized, you'll have sonic chaos. Similarly, poor management of server states can lead to inconsistent data. One component thinks the state is one way, another thinks it's another, and you end up with a dissonant orchestra.

### Uncontrolled Complexity
Server states can become monstrous if you don't keep an eye on them. Poor management can lead to uncontrollable complexity. Components start fighting against each other, and your application becomes an intricate jungle of logic hard to navigate.

### Nightmare Debugging
You know those horror movies where the protagonist tries to escape something but can't because there are No escape routes? Well, imagine having to debug poor state management. It's a bit like being in that movie but without a flashlight.

### Performance Impact
If you let server states get too comfortable, they can impact performance. Unnecessary requests, too frequent updates, and non-optimized data traffic can bog down your application. It's like driving a Ferrari with the brakes on.

### UI Fragility
Poor management can make your user interface as fragile as glass. One state update, and your UI falls like a house of cards.

### Resource Waste
If you don't manage server state well, you'll end up sending unnecessary requests, storing superfluous data, and overall wasting resources. It's like throwing money out the window.

In short, poor management of server states can lead to a series of problems that no developer wants to face. But that's where we come in. In the next sections, we'll see how to avoid these troubles and make server states work in our favor. Ready to fix those glitches? Let's dive in.

## Management and Updating of Server States

To effectively handle Server State over time, various React libraries have emerged, excelling in fetching, caching, and accessing server-side application state fragments.

In this article, I'll show you how TanStack Query (formerly React Query) can come to our rescue (logically, you can use any alternatives you prefer).

Think of TanStack Query as your personal assistant for managing server states. It simplifies fetching data from the server, keeps it in sync with your local state, and frees you from the headaches of typical HTTP requests.

Let's see how we use it in action, focusing on the use of the useQuery hook and the creation of a custom hook to handle data fetching.

### Installation of TanStack Query:

First and foremost, make sure you have TanStack Query installed in your project:

```bash
npm i @tanstack/react-query
```
Now we can use the `useQuery` hook

```jsx
import { useQuery } from '@tanstack/react-query';

const fetchData = async () => {
  const response = await fetch('/api/data');   if (!response.ok) {
    throw new Error('Errore nel recupero dei dati');
  }
  return response.json();
};

function App() {
  const { data, error, isLoading } = useQuery('myData', fetchData);

  if (isLoading) {
    return <p>Loading...</p>;
  }

  if (error) {
    return <p>Error: {error.message}</p>;
  }

  // Now 'data' contain server data.
  return <div>{JSON.stringify(data)}</div>;
}
```
In this example, `useQuery` intelligently handles data fetching from the server. If the data is loading, it will display a loading message. If there are errors, it will show an error message. Otherwise, you'll have access to the updated data.

Now, let's see how to build a custom hook that allows us to "recycle" our fetching logic in an optimal way.

```jsx
import { useQuery } from '@tanstack/react-query';

const useDataFetching = () => {
  const { data, error, isLoading } = useQuery('myData', fetchData);

  return {
    data,
    error,
    isLoading,
  };
};

function App() {
  const { data, error, isLoading } = useDataFetching();

  if (isLoading) {
    return <p>Caricamento...</p>;
  }

  if (error) {
    return <p>Errore: {error.message}</p>;
  }

  return <div>I dati dal server sono: {JSON.stringify(data)}</div>;
}
```
With the custom hook `useDataFetching`, you have a more modular structure. You can reuse it in different parts of your application to handle fetching.

## Let'use the Cache
TanStack Query shines when it comes to cache management too. It uses an intelligent caching system that efficiently stores data, reducing the need for repeated server requests. Let's see how this cache magic works.

### Automatic Cache
By default, TanStack Query automatically saves the results of queries in a local cache. When you request the same data later on, TanStack Query will return the locally stored data instead of making a new request to the server. This not only improves performance but also reduces the load on the server.

### Configurable Cache Policies
You can configure cache policies based on your specific needs. For example, you can set the cache to automatically invalidate data after a certain period or after a change in server-side data. TanStack Query gives you control to adapt the cache to the dynamics of your application.

```js
const { data, error, isLoading } = useQuery('myData', fetchData, {
  cacheTime: 60000, // Invalid after 60 seconds
});
```

## Custom Cache Keys

You can also use custom cache keys to store and retrieve specific data. This is useful when you need to manually manipulate the cache or when working with dynamic data.

```js
useQuery(['myData', { id: 1 }], fetchData);
```

In this example, the cache key becomes `['myData', { id: 1 }]`, and you can access the data using this custom key.

## Cache Clearing
TanStack Query also provides methods to manually clear or invalidate the cache. For instance, you can call `queryClient.invalidateQueries('myData')` to force a new request when needed.

```jsx
import { useQueryClient } from '@tanstack/react-query';

function ClearCacheButton() {
  const queryClient = useQueryClient();

  const handleClick = () => {
    queryClient.invalidateQueries('myData');
  };

  return <button onClick={handleClick}>Invalidate Cache</button>;
}
```
In this way, you have total control over the cache and can tailor it to the specific needs of your application. Tanstack Query makes cache management a smooth and customizable experience. Ready to cache in on this knowledge?

## Conclusions
And with that, we conclude our journey through the intriguing world of server states in React. Now you're armed with knowledge to tackle challenges, manage complexities, and build reactive applications.

You've learned to recognize server states, use Tanstack Query as your trusted ally, and avoid the pitfalls of poor management. Now it's your turn, developer!

If you have questions, concerns, or stories to share about server state management, leave a comment below. The community is here to help and share experiences.

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