无法快速获取downloadURL fire storage的值

Question

I have a struct which gets value about background images from firebase real time database.

struct BackStruct: Identifiable {
    var id = UUID()
    var nameBack, imageUrl, backgroundId: String
}

The problem is that image url in Real time database is just the gs:// address of the image

I am trying to get all URLs to load image on View, but downloadURL closure cannot return string type, even doesn't see global variables in the scope. How can i solve this problem?

for data in self.dataKeys {
    let name = data["nameBack"] as? String ?? ""
    let imageId = data["backgroundId"] as? String ?? ""
    var url = data["imageUrl"] as? String ?? ""
    url = url.components(separatedBy: "appspot.com/").last ?? ""
    
    self.storRef.child(url).downloadURL { (dURL, error) in
        if let error = error {
            print(error)
          } else {
            url = dURL?.absoluteString ?? ""
          }
    }
    
    let img = BackStruct(nameBack: name, imageUrl: url, backgroundId: imageId)
    self.allImages.append(img)
}

Answer 1

The problem is not in getting the URL, but in where you use it. Since the URL is determined asynchronously, you can only use it inside the completion handler.

So:

self.storRef.child(url).downloadURL { (dURL, error) in
    if let error = error {
        print(error)
      } else {
        url = dURL?.absoluteString ?? ""
        let img = BackStruct(nameBack: name, imageUrl: url, backgroundId: imageId)
        self.allImages.append(img)
      }
}