从 Firebase Swift 中读取两个数据模型

Question

我有两个模型：一个User 模型和一本书Review 模型。我在评论中的username 是User 类型，以便我可以检索给定评论和创建它的用户。

我现在可以用我的代码检索评论，但不能检索用户对象。我做错了什么？

用户类

class User: NSObject {
    var id: String?
    var name: String?
    var email: String?
    var profileImageUrl: String?
    init(dictionary: [String: AnyObject]) {
        self.id = dictionary["id"] as? String
        self.name = dictionary["name"] as? String
        self.email = dictionary["email"] as? String
        self.profileImageUrl = dictionary["profileImageUrl"] as? String
    }
}

审查结构

struct Review {
    let id: String
    let bookName: String
    let author: String
    let review: String
    let username: User
    let createdAt: Date
    init(id: String, bookName: String, author: String, review: String, username: User, timestamp: Double) {

        self.id = id
        self.bookName = bookName
        self.author = author
        self.review = review
        self.username = username
        self.createdAt = Date(timeIntervalSince1970: timestamp / 1000)
    }
}

审核员

 private func fetchReviews() {
    let reviewRef = Database.database().reference().child("reviews")
    let queryRef = reviewRef.queryOrdered(byChild: "timestamp").queryLimited(toLast: 5)

    queryRef.observe(.value, with: { snapshot in

        var temporaryReviews = [Review]()

        for child in snapshot.children {
            if let childSnapshot = child as? DataSnapshot,
                let dictionary = childSnapshot.value as? [String:Any],
                let user = dictionary["user"] as? [String:Any],
                let id = user["id"] as? String,
                let name = user["name"] as? String,
                let profileImageUrl = user["profileImageUrl"] as? String,
                let url = URL(string: profileImageUrl),
                let bookName = dictionary["bookName"] as? String,
                let author = dictionary["author"] as? String,
                let review = dictionary["review"] as? String,
                let timestamp = dictionary["timestamp"] as? Double {

                let user = User(dictionary: <#T##[String : AnyObject]#> ??? // Cannot use a user object

                let review = Review(id: childSnapshot.key, bookName: bookName, author: author, review: review, username: user, timestamp: timestamp)

                DispatchQueue.main.async {
                    temporaryReviews.insert(review, at: 0)
                    self.reviews = temporaryReviews
                    self.tableView.reloadData()
                }
            }
        }
    })
}

如果我从循环中删除用户及其关联值，我会在 UI 中获得数据，但不会在我的视图类中更新 username 或 photoImageURL。数据已经在 Firebase 中。如何读取数据和用户？

Answer 1

不清楚这条线的预期是什么

let user = User(dictionary: <#T##[String : AnyObject]#> ???

也不确定为什么 class User: NSObject 是一个 NSObject 但这将适用于 Swift 5。

class User { //using pure Swift, remove NSObject
    var id: String?
    var name: String?
    var email: String?
    var profileImageUrl: String?
    init(dictionary: [String: Any]) { //change AnyObject to Any
        self.id = dictionary["id"] as? String
        self.name = dictionary["name"] as? String
        self.email = dictionary["email"] as? String
        self.profileImageUrl = dictionary["profileImageUrl"] as? String
    }
}

然后在读取闭包中的 Firebase 数据时，创建一个包含要填充用户类的项目的字典

let id = user["id"] as? String,
let name = user["name"] as? String,
let profileImageUrl = user["profileImageUrl"] as? String,
let url = URL(string: profileImageUrl),

let dict: [String: Any] = [
    "id": id,
    "name": name,
    "email": email,
    "profileImageUrl": profileImageUrl
]

let aUser = User(dictionary: dict)

或者您可以将快照传递给 User 类并让它从中获取所需的任何内容

class User {
    var user_id = ""
    var name = ""
    var email = ""
    var profileImageUrl = ""

    init(withSnap: DataSnapshot) {
        self.user_id = withSnap.childSnapshot(forPath: "id").value as? String ?? "No Id"
        self.name = withSnap.childSnapshot(forPath: "name").value as? String ?? "No name"
        self.email = withSnap.childSnapshot(forPath: "email").value as? String ?? "No email"
        self.profileImageUrl = withSnap.childSnapshot(forPath: "profileImageUrl").value as? String ?? "No url"
    }
}

然后

let aUser = User(withSnap: snapshot)

此外，在您的代码中，每次循环迭代都会重新加载 tableView，这可能会导致闪烁。最好的办法是将 self.tableView.reloadData() 移到 for 循环之外，这样它就只执行一次。