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ios - Swift：无法将我的值放入标签（可选问题）

问题描述

我从 Firebase 获得了我的价值，但 Swift 不想把它放在我的标签中。

线程 1：致命错误：在展开可选值时意外发现 nil

总而言之，我的数据库如下所示： Firebase 数据库

我创建了一个标准模型调用 ServiceModel：

import Foundation

class ServiceModel {

    var name: String?
    var category: String?
    var pricing: String?

    init(name: String?, category: String?, pricing: String?){
        self.name = name
        self.category = category
        self.pricing = pricing
    }
}

我想将这些值显示到 TableView 中，所以我创建了一个这样的自定义单元格（也非常标准）：

import UIKit

class SubscriptionTableViewCell: UITableViewCell {

    @IBOutlet weak var imageService: UIImageView!
    @IBOutlet weak var labelName: UILabel!
    @IBOutlet weak var labelCategory: UILabel!
    @IBOutlet weak var labelPricing: UILabel!

    override func awakeFromNib() {
        super.awakeFromNib()
        // Initialization code
    }

    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)

        // Configure the view for the selected state
    }

}

现在，这是我的视图的控制器：

import UIKit
import FirebaseDatabase

class SecondViewController: UIViewController,UITableViewDelegate, UITableViewDataSource {

    var refServices:DatabaseReference!

    @IBOutlet weak var ListSub: UITableView!

    var serviceList = [ServiceModel]()

    var databaseHandle:DatabaseHandle?

    public func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

        return serviceList.count
    }

    public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cell = tableView.dequeueReusableCell(withIdentifier: "SubCell", for: indexPath) as! SubscriptionTableViewCell

        let service: ServiceModel

        service = serviceList[indexPath.row]

        //cell.imageService.image = UIImage(named: service.name! + ".png")
        cell.labelName?.text = service.name //ERROR HERE
        cell.labelCategory?.text = service.category
        cell.labelPricing?.text = service.pricing

        return cell
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        ListSub.delegate = self
        ListSub.dataSource = self

        refServices = Database.database().reference().child("Categories");

        refServices.observe(DataEventType.value, with: { (snapshot) in

            if snapshot.childrenCount > 0 {

                self.serviceList.removeAll()

                for services in snapshot.children.allObjects as! [DataSnapshot] {
                    let serviceObject = services.value as? [String: AnyObject]
                    let serviceName  = serviceObject?["Name"]
                    let serviceCategory  = serviceObject?["Category"]
                    let servicePricing = serviceObject?["Pricing"]
                    let service = ServiceModel(name: serviceName as! String?, category: serviceCategory as! String?, pricing: servicePricing as! String?)

                    self.serviceList.append(service)
                }

                self.ListSub.reloadData()
            }
        })
    }

当我启动这个视图时，我遇到了前面提到的错误。当我调试时，我发现我在 service.name、service.category 和 service.pricing 中有正确的值

似乎我没有正确处理 Optional 值，但我看不出有什么问题。

谢谢你的帮助。

标签： iosswift

解决方案

If you debug this function, what did you see for your service

public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = tableView.dequeueReusableCell(withIdentifier: "SubCell", for: indexPath) as! SubscriptionTableViewCell

    let service: ServiceModel

    //Put a breakpoint here
    service = serviceList[indexPath.row]
    //Put a breakpoint here

    //cell.imageService.image = UIImage(named: service.name! + ".png")
    cell.labelName?.text = service.name
    cell.labelCategory?.text = service.category
    cell.labelPricing?.text = service.pricing

    return cell
}

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