Question

我刚开始使用Cloud Functions for Firebase。我一直坚持从数据库中检索数据。

我在Firebase引用上使用.once('value')将其转换为promise，但每次我使用Postman运行该函数时都会收到此错误：

Error: Can't set headers after they are sent.
at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:357:11)
at ServerResponse.header (/usr/lib/node_modules/firebase-tools/node_modules/express/lib/response.js:725:10)
at ServerResponse.send (/usr/lib/node_modules/firebase-tools/node_modules/express/lib/response.js:170:12)
at ServerResponse.json (/usr/lib/node_modules/firebase-tools/node_modules/express/lib/response.js:256:15)
at Timeout.req.functionTimeout.setTimeout [as _onTimeout] (/usr/lib/node_modules/firebase-tools/node_modules/@google-cloud/functions-emulator/src/supervisor/supervisor.js:192:14)
at ontimeout (timers.js:380:14)
at tryOnTimeout (timers.js:244:5)
at Timer.listOnTimeout (timers.js:214:5)

这是第一个调用函数获取数据的函数：

exports.userPlaylistStatus = functions.https.onRequest(async (request, response) => {
     const userId = request.body.userId;
     // Wait to get the user reference
     const userRef = await buildUserRef(userId);
     response.send(userRef);
});

这是我正在使用.once('value')的函数。承诺永远不会返回值。即使我在console.log('hi')内放置.then()，也永远不会记录。

async function buildUserRef(_userId: string) {
return await admin.database().ref(`/users/${_userId}`).once('value').then(
    // this would return the user reference but I have it as .val() for now
    res => {return res.val();},
    err => {console.log(err)}
);
}

Firebase的云功能 - .once（'value'）不返回任何内容

0 个答案: