在onSubmit中发起呼叫

Question

我是新来的asynch，我想用asynch用firebase，一旦标记设置我想射击的动作，fetchEvents和navigateasync setToken() {    const fcmToken = await firebase.messaging().getToken();    return fcmToken;}onSubmit(e) {    const {        navigation: { navigate },        credentials: { year, group, student },        fetchEvents    } = this.props;    AsyncStorage.setItem(        "loggedIn",        JSON.stringify(this.props.credentials)    );    const token = this.setToken();    if (token) {        fetchEvents(student || group);        navigate("Month");    }}如果我token在调试器中进行检查，那是一个承诺：_40: 0_55: null_65: 0_72: null如何asynch使用我的功能？

Answer 1

每个async函数都返回Promise。就那么简单。

async setToken() {

    const fcmToken = await firebase.messaging().getToken();

    // Now if you console.log() the fcmToken will be string

    return fcmToken;

}

console.log(setToken()) 

// This will be promise and inside will be fcmToken, 

// because anything you return from async function will be wrapped in Promise.

Answer 2

您还需要对await函数进行调用：

async onSubmit(e) {    //  <-- add "async" here

    const {

        navigation: { navigate },

        credentials: { year, group, student },

        fetchEvents

    } = this.props;

    // for that matter, this here being called "AsyncStorage" suggests 

    // that you *might* want to await this too.

    AsyncStorage.setItem(

        "loggedIn",

        JSON.stringify(this.props.credentials)

    );

    const token = await this.setToken();  //  <-- add "await" here

    if (token) {

        fetchEvents(student || group);

        navigate("Month");

    }

}