Apollo Client GraphQL Setup | GraphQL React Apollo Hooks Tutorial 编辑

Apollo gives a neat abstraction layer and an interface to your GraphQL server. You don't need to worry about constructing your queries with request body, headers and options, that you might have done with axios or fetch say. You can directly write queries and mutations in GraphQL and they will automatically be sent to your server via your apollo client instance.

React Apollo Hooks Installation

Let's get started by installing apollo client & peer graphql dependencies:

$ npm install @apollo/client graphql

Create Apollo Client Instance

Open src/components/App.js and add the following imports at the top:

src/components/App.js

import React from 'react';
import Header from './Header';import TodoPrivateWrapper from './Todo/TodoPrivateWrapper';import TodoPublicWrapper from './Todo/TodoPublicWrapper';import OnlineUsersWrapper from './OnlineUsers/OnlineUsersWrapper';
+ import { ApolloClient, ApolloProvider, InMemoryCache, HttpLink } from '@apollo/client';
import { useAuth0 } from "./Auth/react-auth0-spa";
const App = ({ idToken }) => {  const { loading, logout } = useAuth0();  if (loading) {    return <div>Loading...</div>;  }  return (    <div>      <Header logoutHandler={logout} />      <div className="row container-fluid p-left-right-0 m-left-right-0">          <div className="row col-md-9 p-left-right-0 m-left-right-0">            <div className="col-md-6 sliderMenu p-30">              <TodoPrivateWrapper />            </div>            <div className="col-md-6 sliderMenu p-30 bg-gray border-right">              <TodoPublicWrapper />            </div>          </div>          <div className="col-md-3 p-left-right-0">            <div className="col-md-12 sliderMenu p-30 bg-gray">              <OnlineUsersWrapper />            </div>        </div>      </div>    </div>  );};
export default App;

These are the required apollo dependencies to get started. Now let's define a function which will return apollo client with httplink and cache.

import { ApolloClient, ApolloProvider, InMemoryCache, HttpLink } from '@apollo/client';
+ const createApolloClient = (authToken) => {+  return new ApolloClient({+    link: new HttpLink({+      uri: 'https://hasura.io/learn/graphql',+      headers: {+        Authorization: `Bearer ${authToken}`+      }+    }),+    cache: new InMemoryCache(),+  });+ };

Create the apollo client inside App and pass the client prop to <ApolloProvider> component.

const App = ({ idToken }) => {  const { loading, logout } = useAuth0();  if (loading) {    return <div>Loading...</div>;  }+  const [client] = useState(createApolloClient(idToken));   return (+    <ApolloProvider client={client}>       <div>       </div>+    </ApolloProvider>   );};

Let's try to understand what is happening here.

HttpLink and InMemoryCache

We are creating an HttpLink to connect ApolloClient with the GraphQL server. As you know already, our GraphQL server is running at https://hasura.io/learn/graphql

At the end, we instantiate ApolloClient by passing in our HttpLink and a new instance of InMemoryCache (recommended caching solution). We are wrapping all of this in a function which will return the client.

We are going to make use of this function inside App component.