node.js - 从 id 数组中获取 firestore 文档列表

Question

我有一个 firestore 集合，他的值之一是文档 ID 数组。
我需要检索所有集合项以及存储在数组 id 中的所有文档。
这是我收藏的结构


我的代码:

export const getFeaturedMixes = functions.https.onRequest((request, response) => {
    let result:any[] = []
    featuredMixes.get().then(mixesSnap => {

        mixesSnap.forEach(doc => {
            let docId = doc.id
            let ids = doc.data().tracks

            let resultTracks:any[] = []
            ids.forEach(id => {
                let t = tracksCollection.doc(id.track_id).get()
                resultTracks.push({'id' : id.track_id, 'data': t})
            })
            result.push({'id':docId, 'tracks': resultTracks})
        })
        return result
    })
    .then(results => {
        response.status(200).send(results)
    }).catch(function(error) {
        response.status(400).send(error)
    })
});

我得到这个回复:

{
        "id": "Xm4TJAnKcXJAuaZr",
        "tracks": [
            {
                "id": "FG3xXfldeJBbl8PY6",
                "data": {
                    "domain": {
                        "domain": null,
                        "_events": {},
                        "_eventsCount": 1,
                        "members": []
                    }
                }
            },
            {
                "id": "ONRfLIh89amSdcLt",
                "data": {
                    "domain": {
                        "domain": null,
                        "_events": {},
                        "_eventsCount": 1,
                        "members": []
                    }
                }
            }
    ]
}

响应不包含文档数据

Answer 1

get() 方法是异步的并返回一个 Promise。因此，您不能执行以下操作:

 ids.forEach(id => {
      let t = tracksCollection.doc(id.track_id).get()
      resultTracks.push({'id' : id.track_id, 'data': t})
 })

您需要等待 get() 返回的 Promise方法解析，才能使用 t (这是一个 DocumentSnapshot )。

为此，由于您想并行获取多个文档，您需要使用 Promise.all() .

以下应该可以解决问题。请注意，它没有经过测试，您仍然可以轻松完成代码的一部分，请参阅最后的注释。如果您在最终确定时遇到一些问题，请将您的新代码添加到您的问题中。

export const getFeaturedMixes = functions.https.onRequest((request, response) => {
    let result: any[] = []

    const docIds = [];

    featuredMixes.get()
        .then(mixesSnap => {


            mixesSnap.forEach(doc => {
                let docId = doc.id
                let ids = doc.data().tracks

                const promises = []

                ids.forEach(id => {
                    docIds.push(docId);
                    promises.push(tracksCollection.doc(id.track_id).get())
                })

            })

            return Promise.all(promises)
        })
        .then(documentSnapshotArray => {

            // Here documentSnapshotArray is an array of DocumentSnapshot corresponding to
            // the data of all the documents with track_ids

            // In addition, docIds is an array of all the ids of the FeaturedMixes document

            // IMPORTANT: These two arrays have the same length and are ordered the same way

            //I let you write the code to generate the object you want to send back to the client: loop over those two arrays in parallel and build your object


            let resultTracks: any[] = []

            documentSnapshotArray.forEach((doc, idx) => {
                // .....
                // Use the idx index to read the two Arrays in parallel

            })

            response.status(200).send(results)

        })
        .catch(function (error) {
            response.status(400).send(error)
        })
});