ios - 从 firebase 检索对象

Question

我正在开发简单的程序 - 我创建产品对象，然后计算它们的卡路里。

我想计算我的产品所有卡路里的总和。​​

我创建了一个方法，允许我在 Firebase 中正确保存数据，但在检索它们时遇到了困难:

import UIKit
import Firebase

class TotalViewController: UIViewController {

    var products = [Products]()

    @IBOutlet weak var calotyCounter: UILabel!


    override func viewDidLoad() {
        super.viewDidLoad()

        DataService.dataService.PRODUCT_BASE.observeEventType(.Value, withBlock: { snapshot in

            print(snapshot.value)

            self.products = []

            if let snapshots = snapshot.children.allObjects as? [FIRDataSnapshot] {

                for snap in snapshots {

                    if let postDictionary = snap.value as? Dictionary<String, AnyObject> {

                        let key = snap.key

                        let product = Products(key: key, dictionary: postDictionary)


                    }
                }
            }

            self.updateCalory()

        })


        // Do any additional setup after loading the view.
    }

    func updateCalory() {

        var CaloryArray: [Int] = []

        for product in products {

            CaloryArray.append(Int(product.productCalories))

        }

        print (CaloryArray)

        calotyCounter.text? = String(CaloryArray.reduce(0, combine: +))

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

我得到一个空数组，而不是对象调用值数组。

这是我的产品模型。我通过字典制作的

import Foundation
import Firebase

class Products {

    private var _productName: String!

    private var _productCalories: Int!


    var productName: String {

        return _productName

    }

    var productCalories: Int {

        return _productCalories
    }

    init(key: String, dictionary: Dictionary<String, AnyObject>) {


        if let calories = dictionary["calories"] as? Int {

            self._productCalories = calories
        }

        if let name = dictionary["name"] as? String {

            self._productName = name
        }


    }


}

我做错了什么？

Answer 1

您仅在 viewDidLoad() 中启动了 products 的空数组

self.products = []

并且没有在任何地方给它分配任何东西。这就是为什么你得到空数组的原因。

并且在 updateCalory() 方法上，您在空数组(具有零个项目的数组)上循环

编辑 1

您必须附加产品，即

let product = Products(key: key, dictionary: postDictionary)

到循环中的products数组。像这样

for snap in snapshots {

                if let postDictionary = snap.value as? Dictionary<String, AnyObject> {

                    let key = snap.key

                    let product = Products(key: key, dictionary: postDictionary)
                    self. products.append(product) // add this line

                }
            }