single-page-application - 在分配之前使用的 typescript 变量

Question

按照说明遵循 here ，我试图在构建我的 Apollo 客户端之前缓存我的端点 URL 和来自 Auth0 的 token :

import React from 'react';
import { ApolloClient, ApolloProvider, from, HttpLink, InMemoryCache } from '@apollo/client';
import { setContext } from '@apollo/link-context';
import { useAuth0 } from './auth/AuthContext';

const App: React.FC = () => {
	const { isLoading, getTokenSilently, getIdTokenClaims } = useAuth0();

	if (isLoading) return <Loader />;

	let endpoint: string;
	let token: string;
	const contextLink = setContext(async () => {
		if (!token) {
			token = await getTokenSilently();
		}
		if (!endpoint) {
			endpoint = await getIdTokenClaims()['https://example.com/graphql_endpoint'];
		}

		return { endpoint, token };
	});

	/**
	 * TODO: check for autorization error and remove token from cache
	 * See: https://www.apollographql.com/docs/react/v3.0-beta/api/link/apollo-link-context/
	 */

	const apolloClient = new ApolloClient({
		cache: new InMemoryCache(),
		link: from([
			contextLink,
			new HttpLink({
				uri: endpoint || '',
				headers: {
					'Content-Type': 'application/json',
					Authorization: `Bearer ${token}`
				}
			})
		])
	});

	return (
		<ApolloProvider client={apolloClient}>
			<div />
		</ApolloProvider>
	);
};

export default App;

我收到了 endpoint 的错误 TS2454(在分配之前使用了变量)和 token以上。知道如何解决这个问题吗？

Answer 1

您同时声明 endpoint和 token作为变量，但在 setContext 中检查它们之前不要将它们初始化为任何东西。

    let endpoint: string;
    let token: string;
    const contextLink = setContext(async () => {
        if (!token) {
            token = await getTokenSilently();
        }
        if (!endpoint) {
            endpoint = await getIdTokenClaims()['https://example.com/graphql_endpoint'];
        }

        return { endpoint, token };
    });

尝试设置默认值:

let endpoint: string = "";
let token: string = "";