arrays - 追加包含其他类数组的类数组

Question

我有一个通知类数组，它由字符串值和其他 3 个类(用户、照片和视频类)组成。我在将通知类附加到 Collection View 时遇到问题。问题是如果 Photo Class 是空的，它会失败，或者如果 Video Class 是空的，它也无法追加。我已经在 Notification Class 数组中将所有 Classes 设为可选，但它似乎没有什么区别，所以我不确定下一步该做什么。请帮助将不胜感激。提前致谢!

通知数组

class notification { 
    var profilePic: String?
    var fullName: String?
    var descriptionLabel: String?
    var descriptionImage: String?
    var postID: String?
    var user: userAccount?
    var post: Post?
    var videoPost: videoPost?
    var postDescription: String?
    var date: NSNumber?

init (user: userAccount, post: Post, videoPost: videoPost, dictionary: [String: Any]) 
{
            self.videoPost = videoPost
            self.post = post
            self.user = user
            self.postDescription =  dictionary["postDescription"] as? String ?? ""
            self.fullName =  dictionary["fullName"] as? String ?? ""
            self.profilePic =  dictionary["profilePic"] as? String ?? ""
            self.descriptionLabel =  dictionary["textDesciption"] as? String ?? ""
            self.descriptionImage =  dictionary["desciptionImage"] as? String ?? ""
            self.postID =  dictionary["postID"] as? String ?? ""
            self.date = dictionary["notificationDate"] as? NSNumber       
        }

Collection View Controller

func loadData(){

   let userID = Auth.auth().currentUser!.uid
    Database.database().reference().child("notification").child(userID).observe(.childAdded, with: { (snapshot) in
        guard let dictionary = snapshot.value as? [String: Any] else { return }
        let uid = dictionary["uid"] as? String
        let postId = dictionary["postID"] as? String

        Database.fetchUserWithUID(uid: uid!, completion: { (snapshot) in
            Database.fetchPostWithUID(uid: userID, postId: postId!, completion: { (postShot) in
                Database.fetchVideoPostWithUID(uid: userID, postId: postId!, completion: { (videoShot) in

                    let comment = notification(user: snapshot, post: postShot, videoPost: videoShot, dictionary: dictionary)
                    self.notifications.append(comment)
                    self.notificationTableView?.reloadData()
                })
            })
        })
    })
}

extension Database {

    static func fetchUserWithUID(uid: String, completion: @escaping (userAccount) -> ()) {
        Database.database().reference().child("user").child(uid).observeSingleEvent(of: .value, with: { (snapshot) in

        let user = userAccount(snapshot:snapshot)
         completion(user)
            })
    }

    static func fetchPostWithUID(uid: String, postId: String,  completion: @escaping (Post) -> ()) {
        Database.database().reference().child("post").child(uid).child(postId).observeSingleEvent(of: .value, with: { (snapshot) in

            if snapshot.exists() {
                let post = Post(snapshot:snapshot)
                completion(post)
            }else{
        // Not sure what to write here when snapshot is equal to nil

        })
}

  static func fetchVideoPostWithUID(uid: String, postId: String,  completion: @escaping (videoPost) -> ()) {
        Database.database().reference().child("videoPost").child(uid).child(postId).observeSingleEvent(of: .value, with: { (snapshot) in

            if snapshot.exists(){          
            let post = videoPost(snapshot:snapshot)
            completion(post)
            }else{
        // Again not sure what to write here when snapshot is equal to nil

            }            
        })
}

Answer 1

您的代码存在多个问题。我会一一道来:

您正在级联中从 Firebase 获取数据。因此，首先获取 user，然后是 photo，最后是 video。

在您的方法 fetch(Post|Video)withUUID 中，您调用完成 block if 返回结果，否则您什么都不做。这意味着，下一个方法/ block 将永远不会被调用。

一种修复方法:

init (user: userAccount, post: Post?, videoPost?: videoPost, dictionary: [String: Any]) {
   // your code after
}

static func fetchPostWithUID(uid: String, postId: String,  completion: @escaping (Post?) -> ()) {
  Database.database().reference().child("post").child(uid).child(postId).observeSingleEvent(of: .value, with: { (snapshot) in

    if snapshot.exists() {
      let post = Post(snapshot:snapshot)
      completion(post)
    }else{
      completion(nil)
    })
  }

static func fetchVideoPostWithUID(uid: String, postId: String,  completion: @escaping (videoPost?) -> ()) {
    Database.database().reference().child("videoPost").child(uid).child(postId).observeSingleEvent(of: .value, with: { (snapshot) in
      if snapshot.exists(){
        let post = videoPost(snapshot:snapshot)
        completion(post)
      }else{
        completion(nil)
      }
    })
}

对您的代码进行几处更改:

1. post 和 videoPost 现在在完成 block 中是可选的 (?):@escaping (Post?) 代替 @escaping (Post)，@escaping (videoPost?) 代替 @escaping (videoPost )

2. 如果您没有结果，它仍会调用带有 nil 值的完成 block :completion(nil)