试图在firebase上实现云函数，但未定义的变量出现错误

Question

我在firebase项目中实现了下面的函数，并将其部署到我的云函数中，但在执行时，它会导致firebase控制台的函数日志中出现错误；

> TypeError: Cannot read property 'profileImgUrl' of undefined

我理解它产生的错误的含义，但我不明白为什么我的用户变量会是未定义的

以下是功能：

exports.eventInvites = functions.firestore
.document('Events/{eventId}').onCreate((snap, context) => {
const eventData = snap.data();
const eventId = context.params.eventId;
const invitees = eventData.invitees;
let user;
db.doc(`Users/${eventData.createdBy}`).get().then(doc => {
var data = doc.data();
user = data; // updated user data but still get undefined
return user;
}).catch(error => {
console.log(error.message);
});
if (invitees !== undefined || invitees.length > 0) {
invitees.forEach(invitee => {
db.collection('Users').doc(invitee).collection('feed').doc().set({
date: new Date(),
image: user.profileImgUrl, // error occurs here, says user is undefined
summary: `${user.firstName} ${user.lastName} invited you to an event`,
extraText: `${eventData.eventName}: ${eventData.eventDetails} `,
extraImages: [
eventData.eventImgUrl
]
}).catch(error => {
console.log(error.message)
});
});
}
});

Answer 1

get()是异步的，因此它之后的代码在之前执行。为了解决这个问题，您可以将所有代码放入get():中

db.doc(`Users/${eventData.createdBy}`).get().then(doc => {
var data = doc.data();
user = data;
if (invitees !== undefined || invitees.length > 0) {
invitees.forEach(invitee => {
db.collection('Users').doc(invitee).collection('feed').doc().set({
date: new Date(),
image: user.profileImgUrl,
summary: `${user.firstName} ${user.lastName} invited you to an event`,
extraText: `${eventData.eventName}: ${eventData.eventDetails} `,
extraImages: [
eventData.eventImgUrl
]
})
});
}
return user;
}).catch(error => {
console.log(error.message);
});