swift - 如何在 swift 中进行顺序 firebase 查询？

Question

下面是我的数据结构:

{    
    "posts": {

        "xyz1": {
          "author": "Jan",
          "uid": "abc123",
        },
        "xyz2": {
          "author": "Jenny",
          "uid": "abc456",
        },

      }

    "users": {
        "abc123": {
          "email": "Jan@gmail.com",
          "profilePicURL": "https://firebasestorage.googleapis.com/v0/b/",
        },
        "abc456": {
          "email": "Jenny@gmail.com",
          "profilePicURL": "https://firebasestorage.googleapis.com/v0/c/",
        },
      }    
}

我想在表格 View 中显示“帖子”条目列表。

 let postRef = ref.child("posts")

        postRef.observe(.childAdded, with: { (snapshot) in
            let authorText = snapshot.value!.object(forKey: "author") as! String
            let userIDText = snapshot.value!.object(forKey: "uid") as! String
            }) { (error) in
                print(error.localizedDescription)
            }

我如何使用从上述查询中检索到的“uid”进行顺序查询，以使用“users”中的“uid”值检索“profilePicURL”。最终目标是在表格 View 中显示存储在帖子旁边的个人资料图片。

感谢您提供的任何帮助。

Answer 1

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {


    let cell = tableView.dequeueReusableCell(withIdentifier: "HomeCell", for: indexPath) as! HomeTableViewCell

    cell.author.text = String(self.author[(indexPath as NSIndexPath).row])    
    let userIDText = String(self.userID[(indexPath as NSIndexPath).row])

    ref.child("users").child(userIDText).observeSingleEvent(of: .value, with: { (snapshot) in
        print("snaphot is \(snapshot)")
        let imageLink = snapshot.value?["profileImageUrl"] as! String
        self.storageRef = FIRStorage.storage().reference(forURL: imageLink)

        cell.profilePic.loadImageUsingCacheWithUrlString(urlString: imageLink)

    }) { (error) in
        print(error.localizedDescription)
    }
    return cell      
}

我使用 UIImageView 的以下扩展来使用 URL 加载图像并且它有效!!

 let imageCache = NSCache<AnyObject, AnyObject>()

        extension UIImageView {

            func loadImageUsingCacheWithUrlString(urlString: String) {

            self.image = nil

            //check cache for image first
            if let cachedImage = imageCache.object(forKey: urlString) as? UIImage {
                self.image = cachedImage
                return
            }

            //otherwise fire off a new download
            let url = NSURL(string: urlString)
            URLSession.shared.dataTask(with: url! as URL, completionHandler: { (data, response, error) in

                //download hit an error so lets return out
                if error != nil {
                    print(error)
                    return
                }

                DispatchQueue.main.async(execute: {

                    if let downloadedImage = UIImage(data: data!) {
                        imageCache.setObject(downloadedImage, forKey: urlString)

                        self.image = downloadedImage
                    }
                })

            }).resume()
        }

    }