你好,当我从 react 中的另一个组件调用 Auth.isAuthenticated(( 时,我有这个类,它总是返回 false(这是默认值(,即使服务器返回 200 响应,女巫也会设置这个。如何使用 promise 使方法等到获取调用完成,然后返回结果
编辑:我需要返回布尔值 true 或 false,因此基于此,我可以显示或隐藏组件,所有答案都有帮助,但我需要一个布尔值而不是承诺任何帮助
class Auth {
constructor() {
this.authenticated = false;
}
isAuthenticated() {
//get token from local storage if there is one
const jwttoken = localStorage.getItem('jwttoken');
const bearer = 'Bearer ' + jwttoken;
const data = new FormData();
// get the website backend main url from .env
const REACT_APP_URL = process.env.REACT_APP_URL
fetch(`${REACT_APP_URL}/api/auth/verify`, {
method: 'POST',
headers: {
'Accept': 'application/json',
'Authorization': bearer,
},
body: data
}).then(
(response) => {
response.json()
.then((res) => {
if (response.status === 200) {
this.authenticated = true;
}
if (response.status === 401) {
localStorage.removeItem('jwttoken');
this.authenticated = false;
}
})
}
).catch((err) => {
// console.log(err)
});
return this.authenticated;
}
}
export default new Auth();
从另一个组件调用 Auth.isAuthenticated(( === true
export const PrivateRoute = ({ component: Component, ...rest }) => {
return (
<Route {...rest} render={(props) => (
Auth.isAuthenticated() === true
? <Component {...props} />
: <Redirect to='/admin' />
)} />
)
}
假设您要编写一个函数,该函数返回一个 promise,并在某些操作完成时进行解析(例如 API 调用(。你可以写这样的东西:
const myAsyncFunction = () =>{
return new Promise((resolve, reject) =>{
//Faking an API Call
setTimeout(() => resolve('data'), 400)
})
}
给你!现在你有一个函数,它返回一个承诺,该承诺将在 400 毫秒内解析。现在,您需要使用.then()
方法或async await
语句。
const sideEffects = async () =>{
const result = await myAsyncFunction()
console.log(result) //'data'
}
不想做async/await
你可以让isAuthenticated
回报一个承诺。
isAuthenticated() {
return new Promise((resolve, reject) => {
//get token from local storage if there is one
const jwttoken = localStorage.getItem('jwttoken');
const bearer = 'Bearer ' + jwttoken;
const data = new FormData();
// get the website backend main url from .env
const REACT_APP_URL = process.env.REACT_APP_URL
fetch(`${REACT_APP_URL}/api/auth/verify`, {
method: 'POST',
headers: {
'Accept': 'application/json',
'Authorization': bearer,
},
body: data
}).then(
(response) => {
response.json()
.then((res) => {
if (response.status === 200) {
resolve(true)
}
if (response.status === 401) {
localStorage.removeItem('jwttoken');
resolve(false)
}
})
}
).catch((err) => {
// reject(err)
});
})
}
在异步函数中,您可以执行let isAuthenticated = await isAuthenticated()
或者您可以使用异步函数之外的.then
和.catch
返回结果
使用 await async
async isAuthenticated() {
//get token from local storage if there is one
const jwttoken = localStorage.getItem('jwttoken');
const bearer = 'Bearer ' + jwttoken;
const data = new FormData();
// get the website backend main url from .env
const REACT_APP_URL = process.env.REACT_APP_URL
const response = await fetch(`${REACT_APP_URL}/api/auth/verify`, {
method: 'POST',
headers: {
'Accept': 'application/json',
'Authorization': bearer,
},
body: data
});
const responseToJson = await response.json();
if (responseToJson.status === 200) {
this.authenticated = true;
}
if (responseToJson.status === 401) {
localStorage.removeItem('jwttoken');
this.authenticated = false;
}
return this.authenticated;
}