Firebase将快照值转换为对象 [英] Firebase converting snapshot value to objects

问题描述

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

有没有一个快速的方法来将postDict转换为Post对象的数组，以便在出列单元格时，它将是：

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

 导入UIKit 
导入Firebase 
 
 class ViewController：UIViewController {
 
 var posts = [Post]（）
 
覆盖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）
 
 //将postDict转换为Post对象的数组
}）
} 
} 
 
 class Post：NSObject {
 var author：String =
 var body ：String =
 var imageURL：String =
 var uid：String =
} 
  

这是输出postDict时的输出：

尝试使用我在下面创建的类，协议和扩展名，它将为您节省大量时间，试图将快照映射到对象。

  // 
 // FIRDataObject.swift 
 // 
 //由Callam Poynter创建24 / 06/2016。 
 // 
 
导入Firebase 
 
类FIRDataObject：NSObject {
 
让snapshot：FIRDataSnapshot 
 var key：String {返回snapshot.key} 
 var ref：FIRDatabaseReference {return snapshot.ref} 
 
 init（快照：FIRDataSnapshot）{
 
 self.snapshot =快照
 
 super.init（）
 
在snapshot.children.allObjects中作为child？ [FIRDataSnapshot] ?? [] {
 if respondsToSelector（Selector（child.key））{
 setValue（child.value，forKey：child.key）
} 
} 
} 
 
 
协议FIRDatabaseReferenceable {
 var ref：FIRDatabaseReference {get} 
} 
 
扩展FIRDatabaseReferenceable {
 var ref：FIRDatabaseReference {
 return FIRDatabase.database（）。reference（）
} 
} 
  

现在可以创建一个继承FIRDataObject类的模型，并可以使用FIRDataSnapshot初始化。然后将FIRDatabaseReferenceable协议添加到您的ViewController中，以访问您的基础引用。

 导入Firebase 
导入UIKit 
 $ b $ class ViewController：UIViewController，FIRDatabaseReferenceable {
 
 var post：[Post] = [] 
 
覆盖func viewDidLoad（）{
 
 super.viewDidLoad（）
 
 ref.child（posts）。observeEventType（.ChildAdded，withBlock：{
 self.posts.append（Post（snapshot：$ 0））$ 
 
 
 
 
 
 
 
 
 
 
 $ body $  
 
 
 $ b $对于Swift 3来说，更新     
 
 
  class FIRDataObject ：NSObject {
 
 let snapshot：FIRDataSnapshot 
 var key：String {return snapshot.key} 
 var ref：FIRDatabaseReference {return snapshot.ref} 
 
需要init（快照：FIRDataSnapshot）{
 
 self.snapshot =快照
 $ b super.init（）
 
 .children.allObjects as？ [FIRDataSnapshot] ?? [] {
 if responds（to：Selector（child.key））{
 setValue（child.value，forKey：child.key）
} 
} 
 } 
} 
  
 
So I have a postDict as [String: AnyObject] and I have a model class Post. 

Is there a quick way to convert postDict to an array of Post objects so that when dequeuing the cell, it will be:

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 = ""
}
This is the output when printing out postDict:

解决方案
Try using the class, protocol and extension I have created below, it will save you a lot of time trying to map the snapshots to objects.
//
//  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()
    }
}
Now you can create a model that inherits the FIRDataObject class and can be initialised with a FIRDataSnapshot. Then add the FIRDatabaseReferenceable protocol to your ViewController to get access to your base reference.
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 = ""
}
UPDATE for 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)
            }
        }
    }
}


                        
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