swift – Firebase将快照值转换为对象

发布时间：2020-12-14 05:34:47 所属栏目：百科来源：网络整理

导读：所以我有一个postDict作为[String：AnyObject],我有一个模型类Post. 有没有一种快速的方法来将PostDict转换为一个Post对象数组,以便在对单元格进行排队时,它将是： cell.textLabel.text = posts [indexPath.item] .author import UIKitimport Firebaseclass

所以我有一个postDict作为[String：AnyObject],我有一个模型类Post.

有没有一种快速的方法来将PostDict转换为一个Post对象数组,以便在对单元格进行排队时,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：

尝试使用下面创建的类,协议和扩展名,它会节省大量时间尝试将快照映射到对象.

//
//  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类的模型,并可以使用FIRDataSnapshot进行初始化.然后将FIRDatabaseReferenceable协议添加到您的ViewController以访问您的基准引用.

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 = ""
}

Swift 3的更新

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)
            }
        }
    }
}

（编辑：李大同）

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