从 Firebase 加载图像非常慢

Question

I am fairly new to Swift development, and am wondering why it is taking so long for the image to show. It's a 4.44kb image whose URL is stored in a Firestore document. It takes a second before it shows, which isn't very good for the UX. As I said, the image (a barcode) is just 4.44kb, which makes me wonder why loading for example an image from Instagram or Facebook is faster than loading this image.

My code:

In my viewDidLoad:

dbRef.getDocument { (document, err) in
        if let e = err {
            print("Error retrieving document: \(e)")
        } else {
            let data = document?.data()
            
            if let imageURL = data?[K.User.barcodeImage] as? String {
                // let url = URL(fileURLWithPath: imageURL)
                let url = NSURL(string: imageURL)
                self.downloadImage(from: url as! URL)
                let number = data![K.User.barcodeNumber] as! String
                self.cardNumber.text = number
                UserDefaults.standard.set(number, forKey: K.User.barcodeNumber)
                UserDefaults.standard.synchronize()
            }
            
            
        }
    }

The rest:

func getData(from url: URL, completion: @escaping (Data?, URLResponse?, Error?) -> ()) {
    URLSession.shared.dataTask(with: url, completionHandler: completion).resume()
}

func downloadImage(from url: URL) {
    getData(from: url) { data, response, error in
        guard let data = data, error == nil else { return }
        DispatchQueue.main.async() { [weak self] in
            self?.cardCode.image = UIImage(data: data)
        }
    }
}

Does this have to do with DispatchQueue? Thank you in advance!

Answer 1

The 1 second latency is not unreasonable but you can try enabling cache headers from firebase storage / GCS bucket to improve performance.