Use React Query and database for data cache merging

Introduction:
In modern front-end development, data management is a very important part. In order to improve performance and user experience, we usually need to cache the data returned by the server and merge it with local database data. React Query is a very popular data caching library that provides a powerful API to handle querying, caching, and updating data. This article will introduce how to use React Query and a database for data cache merging, and provide specific code examples.

Step 1: Install and configure React Query
First, we need to install React Query. Open a terminal and execute the following command:

npm install react-query
or
yarn add react-query
Next, create a React Query configuration file in our project. Create a file named react-query-config.js in the src directory and add the following content:

import { QueryClient, QueryClientProvider } from 'react-query';

const queryClient = new QueryClient();

export const QueryClientProviderWrapper = ({ children }) => (

{children}

);
Here we create an instance named queryClient and pass it to the QueryClientProvider component. This way we can use React Query throughout the project.

Step 2: Create data API
Now we need to create a data API to get the data on the server and cache it into React Query. Suppose our API provides a getItems() method that gets a list of items and returns an array containing all the items. Create a file named api.js in the src directory and add the following content:

import { queryClient } from './react-query-config';

export const getItems = async () => {
// Get item data from the server
const response = await fetch('/api/items');
const data = await response.json();

// Cache data into React Query
queryClient.setQueryData('items', data);

return data;
};
Here we use the fetch() method Get the data from the server and cache the data into React Query using the queryClient.setQueryData() method.

Step 3: Create a database API
Next, we need to create a database API to obtain data from the local database. Suppose our database provides a getItemsFromDatabase() method to get a list of items in the database and return an array containing all the items. Create a file named database.js in the src directory and add the following content:

export const getItemsFromDatabase = () => {
// Get item data from the database
const items = ...

return items;
};
In actual applications, you need to implement the getItemsFromDatabase() method according to the database type and corresponding library you use.

Step 4: Merge Data
Now, we can use React Query and the database API to merge the data. In our component, we use the useQuery() hook to get the data and the useMutation() hook to handle updates to the data. Here is a basic example component:

import { useQuery, useMutation } from 'react-query';
import { getItems, getItemsFromDatabase } from './api';

const ItemList = () => {
// Use useQuery hook to get data
const { data: serverData } = useQuery('items', getItems);
const { data: databaseData } = useQuery( 'itemsFromDatabase', getItemsFromDatabase);

//Use useMutation hook to handle data updates
const { mutate } = useMutation(() => {

// 在這里使用數(shù)據(jù)庫API更新數(shù)據(jù)

});

// Merge cache data and database data
const mergedData = [...serverData, ...databaseData];

return (

<div>
  {mergedData.map((item) => (
    <div key={item.id}>{item.name}</div>
  ))}
</div>

);
};
Here, we use two useQuery hooks to get data from the server and the database respectively (by passing 'items' and 'itemsFromDatabase' as query keys). We then use the useMutation hook to handle updates to the data. Finally, we merge the cache data with the database data and display it in the component.

Summary:
Using React Query and database for data cache merging can greatly improve application performance and user experience. In this article, we learned how to install and configure React Query, and use React Query and the database API to get and update data. I hope this article was helpful and if you have any questions, please feel free to ask!

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