swift - Firebase 将快照值转换为对象

Question

所以我有一个 postDict 作为 [String: AnyObject] 并且我有一个模型类 Post。

有没有一种快速的方法可以将 postDict 转换为 Post 对象的数组，以便在单元格出队时，它将是:

cell.textLabel.text = posts[indexPath.item].author

import UIKit
import Firebase

class ViewController: UIViewController {

var posts = [Post]()

override func viewDidLoad() {
    super.viewDidLoad()

    let ref = FIRDatabase.database().reference().child("posts").queryLimitedToFirst(5)

    ref.observeEventType(FIRDataEventType.ChildAdded, withBlock: { (snapshot) in
        let postDict = snapshot.value as! [String : AnyObject]

        print(postDict)          

        //convert postDict to array of Post objects
    })
  }
}

class Post: NSObject {
    var author: String = ""
    var body: String = ""
    var imageURL: String = ""
    var uid: String = ""
}

这是打印 postDict 时的输出:

Answer 1

尝试使用我在下面创建的类、协议(protocol)和扩展，它将为您节省大量尝试将快照映射到对象的时间。

//
//  FIRDataObject.swift
//
//  Created by Callam Poynter on 24/06/2016.
//

import Firebase

class FIRDataObject: NSObject {

    let snapshot: FIRDataSnapshot
    var key: String { return snapshot.key }
    var ref: FIRDatabaseReference { return snapshot.ref }

    required init(snapshot: FIRDataSnapshot) {

        self.snapshot = snapshot

        super.init()

        for child in in snapshot.children.allObjects as? [FIRDataSnapshot] ?? [] {
            if respondsToSelector(Selector(child.key)) {
                setValue(child.value, forKey: child.key)
            }
        }
    }
}

protocol FIRDatabaseReferenceable {
    var ref: FIRDatabaseReference { get }
}

extension FIRDatabaseReferenceable {
    var ref: FIRDatabaseReference {
        return FIRDatabase.database().reference()
    }
}

现在您可以创建一个继承 FIRDataObject 类并可以使用 FIRDataSnapshot 进行初始化的模型。然后将 FIRDatabaseReferenceable 协议(protocol)添加到您的 ViewController 以访问您的基本引用。

import Firebase
import UIKit

class ViewController: UIViewController, FIRDatabaseReferenceable {

    var posts: [Post] = []

    override func viewDidLoad() {

        super.viewDidLoad()

        ref.child("posts").observeEventType(.ChildAdded, withBlock: {
            self.posts.append(Post(snapshot: $0))
        })
    }
}

class Post: FIRDataObject {

    var author: String = ""
    var body: String = ""
    var imageURL: String = ""
}

更新 Swift 3

class FIRDataObject: NSObject {

    let snapshot: FIRDataSnapshot
    var key: String { return snapshot.key }
    var ref: FIRDatabaseReference { return snapshot.ref }

    required init(snapshot: FIRDataSnapshot) {

        self.snapshot = snapshot

        super.init()

        for child in snapshot.children.allObjects as? [FIRDataSnapshot] ?? [] {
            if responds(to: Selector(child.key)) {
                setValue(child.value, forKey: child.key)
            }
        }
    }
}