异步函数返回未定义

Question

我是async await的新手-我正在尝试在const tokenSet = await setToken(credentials);动作中使用fetchEvents，但是tokenSet始终是未定义的。

如何返回fcmToken作为要在操作中使用的值？

async function setToken(credentials) {
    const { year, group, student } = credentials;
    const fcmToken = await firebase.messaging().getToken();

    if (fcmToken) {
        firebase
            .firestore()
            .collection("users")
            .doc(fcmToken)
            .set({
                year, group, student
            })
            .then(function(fcmToken) {
                return fcmToken;
            })
            .catch(function(error) {
                return null;
            });
    }
}

我在这里使用setToken函数：

export function fetchEvents(credentials) {
    const { year, group, student } = credentials;
    const currentDateString =
        moment().format("YYYY-MM-DD") + "T" + "07:00:00.000Z";
    const id = student || group;
    const url = `https://www.googleapis.com/calendar/v3/calendars/${id}/events?singleEvents=true&orderBy=startTime&timeMin=${currentDateString}&key=${key}`;

    return async dispatch => {
        dispatch(isLoading(true));
        console.log();
        const tokenSet = await setToken(credentials);

        if (tokenSet) { // always undefined
            fetch(url)
                .then(response => {
                    return response;
                })
                .then(response => response.json())
                .then(data => {
                    const { error } = data;
                    if (error) {
                        dispatch(hasErrored(error.message));
                    } else {
                        dispatch(fetchSuccessEvents(data.items));
                    }

                    navigate("Month");
                    dispatch(isLoading(false));
                });
        }
    };
}

Answer 1

尝试一下：

async function setToken(credentials) {
    const { year, group, student } = credentials;
    const fcmToken = await firebase.messaging().getToken();

    if (fcmToken) {
        firebase
            .firestore()
            .collection("users")
            .doc(fcmToken)
            .set({
                year, group, student
            })
            .then(function(fcmToken) {
                return fcmToken;
            })
            .catch(function(error) {
                return null;
            });
        return true;
    }
    return false;
}