如何在 Firebase 中获取日期

Question

Source code shown below,

Database:

static func insertErrorLog(moduleName: String, message: String) {
    let dateToday = Date()
    let timestamp = Int(Date().timeIntervalSince1970)

    let db = Firestore.firestore()

    let docData: [String: Any] = [
        KDB.Fields.moduleName : moduleName,
        KDB.Fields.message : message,
        KDB.Fields.createdAt : dateToday
    ]

Model:

var uploadedAt: String = ""
var createdAt: String = ""

init(document: DocumentSnapshot) {
    self.key = document.documentID

    let json = JSON(document.data())

    self.storeId = json[KDB.Fields.storeId].stringValue
    self.imgName = json[KDB.Fields.imgName].stringValue
    self.title = json[KDB.Fields.title].stringValue
    self.description = json[KDB.Fields.description].stringValue
    self.sort = json[KDB.Fields.sort].intValue
    self.uploadedAt = json[KDB.Fields.uploadedAt].stringValue
    self.createdAt = json[KDB.Fields.createdAt].stringValue
}

init(key: String, storeId: String, imgName: String, title: String, description: String, sort: Int, uploadedAt: String, createdImageAt: String = "") {
    self.key = key
    self.storeId = storeId
    self.imgName = imgName
    self.title = title
    self.description = description
    self.sort = sort
    self.uploadedAt = uploadedAt
    self.createdAt = createdImageAt
}

Controller:

    query.getDocuments { (querySnapshot, error) in
        if let error = error {
            SpeedLog.print("Error: \(error.localizedDescription)")
        } else {
            var loop = 1
            for document in (querySnapshot?.documents)! {
                SpeedLog.print("documentDATA:\(document.data())")
                var photoObject = Photo(document: document)
                SpeedLog.print("photoObject:\(photoObject)")

                if (!photoObject.imgName.isEmpty) {
                    let storagePath = "\(photoObject.imgName)"
                    SpeedLog.print("Photo storagePath: \(storagePath)")

                    let storage = Storage.storage()
                    let storageRef = storage.reference()
                    let imageRef = storageRef.child(storagePath)

                    imageRef.getData(maxSize: 1 * 1024 * 1024) { data, error in
                        if let error = error {
                            SpeedLog.print("Photos download image error documentID:\(document.documentID) : \(error.localizedDescription)")
                        } else {
                            photoObject.imageData = UIImage(data: data!)
                            self.photos.append(photoObject)

                            if loop == 1 {
                                self.imageView.image = photoObject.imageData!
                                self.photoTitleLabel.text = "\(photoObject.title)"

                                    self.photoCreatedAtLabel.text = "\(photoObject.createdAt)"
                                    self.photoCreatedAtTitleLabel.isHidden = false
                                //}
                            }
                        }
                        self.collectionView.reloadData()
                        loop += 1
                    }
                }
            }
        }
    }
}

extension PhotoGalleryViewController: UICollectionViewDataSource, UICollectionViewDelegate {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return photos.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CellPhotoGallery", for: indexPath) as! PhotoGalleryCollectionViewCell

    configureCell(cell, atIndexPath: indexPath)

    return cell
}

func configureCell(_ cell: PhotoGalleryCollectionViewCell, atIndexPath indexPath: IndexPath) {

    let photo = photos[indexPath.row]

    if let image = photo.imageData {
        cell.imageView.image = image
    }
    photoLabel.text = photo.title
    photoCreatedAtLabel.text = photo.createdAt
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    let photo = photos[indexPath.row]

    if let image = photo.imageData {
        imageView.image = image
    }
    photoLabel.text = photo.title
    photoCreatedAtLabel.text = photo.createdAt
}

In Firebase we have field createdAt: (Timestamp)

Basically, when I run the codes in Xcode the Photo Storage fetch the createdAt from the firebase data but when it comes to Photo Object"self.photoCreatedAtLabel.text = "(photoObject.createdAt)" the date didn't shown. What is the possible missing in the codes? Please see attached of application for reference.

Edit: added a console printout of the photo object.

photoObject:Photo (
   key: "x2q0Asfjn2S8FYr6fIvA", 
   storeId: "", 
   imgName: "locator/stores/egdupo/BitoysVulcanizingandTireShop_rJTM7alkTp_M6L.jpg", 
   imageData: nil, 
   title: "", 
   description: "", 
   sort: 1, 
   uploadedAt: "", 
   createdAt: ""
)

Anyone?

Thank you in advance.

Answer 1

From the FireStore docs

Currently, Firestore returns timestamp fields as Date but Date only supports millisecond precision, which leads to truncation and causes unexpected behavior when using a timestamp from a snapshot as a part of a subsequent query.

So if you want to use it, your code needs to handle it as a NSDate (Date) object. however, using the following code

let settings = Firestore.firestore().settings
settings.areTimestampsInSnapshotsEnabled = true

Setting timestampsInSnapshots to true will cause Firestore to return Timestamp values instead of Date, which avoids truncation. Note that you must also change any code that uses Date to use Timestamp instead.

In practice, assume we have a collection of documents and one of the fields in each document is called stamp; written like this

let now = Date()
let stamp = Timestamp(date: now)
self.db.collection("timestamps").document("test_stamp_0").setData( [
   "stamp": stamp
])

to then read that stamp node and format it for output in a UI

//read the document
if let stamp = document.get("stamp") {
    let title = document.documentID
    let ts = stamp as! Timestamp //force downcast stamp to a Timestamp cause' that's what it is.
    let aDate = ts.dateValue()
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd HH:mm:ss ZZZ"
    let formattedTimeZoneStr = formatter.string(from: aDate)
    print(title, formattedTimeZoneStr) //prints test_stamp_0, 2018-10-03 08:00:00 -0400
}