Firebase Cloud Functions对象可能“未定义" [英] Firebase Cloud Functions Object possibly 'undefined'

问题描述

我在打字稿中有以下代码，并且在行上遇到此错误:change.after.data();，对象可能是未定义":

I have the following code in typescript and i get this error on the line: change.after.data();, Object is posibbly 'undefined':

import * as functions from 'firebase-functions'
import * as admin from 'firebase-admin'

admin.initializeApp()

export const onEditModeUpdate = 
functions.firestore.document("Settings/ShiftsEditMode").onUpdate(change=> {
    const after = change.after.data();
    const payload = {
        data: {
            temp: String(after.temp),
            conditions: after.conditions
        }
    }
    return admin.messaging().sendToTopic("Settings/ShiftsEditMode", payload)
})

我想要做的是，只要firestore中的某些内容发生变化，就向我的应用发送通知，我遵循了官方文档，但出现错误，我认为这与node.js版本有关.有什么帮助吗?

what I want to do is to send to my app a notification whenever something in firestore changes, I followed the official documentation but I get the error, I think this has to do with node.js version. Any help, please?

推荐答案

您的change参数的类型为Change.如果在VSCode中单击它，您将在这里看到它的定义:

Your change parameter is of type Change. If you click through to it in VSCode, you'll see it's definition here:

export declare class Change<T> {
    before?: T;
    after?: T;
    constructor(before?: T, after?: T);
}

请注意，它的before和after属性都是可选的，并在类型中标有?.这意味着可能未定义值.

Notice that its before and after properties are both optional, marked with a ? in the type. This means that it's possible that the values are undefined.

tsconfig.json中的TypeScript配置很可能包含"strict": true的行，该行告诉TypeScript每当您尝试访问未明确检查而未定义的属性时都不会警告您.那就是你在这里看到的错误.

It's likely that your TypeScript config in tsconfig.json contains a line for "strict": true, which tells TypeScript not warn you whenever you try to access a property that could be undefined without explicitly checking it first. That's the error you're seeing here.

您有两个选择:

1)从tsconfig.json中删除该行

1) Remove that line from your tsconfig.json

2)或检查是否首先定义了

2) Or check to see if it's defined first

if (change.after) {
    const after = change.after.data();
    const payload = {
        data: {
            temp: String(after.temp),
            conditions: after.conditions
        }
    }
    return admin.messaging().sendToTopic("Settings/ShiftsEditMode", payload)
}
else {
    return null;
}

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