ios - Swift:无法将我的值放入标签(可选问题)

Question

我从 Firebase 获得了自己的值(value)，但 Swift 不想将其放入我的标签中。

Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value

总而言之，我的数据库如下所示: Firebase database

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
    }
}

我想将此值显示到 TableView 中，因此我创建了一个像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 View 的 Controller :

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()
            }
        })
    }

当我启动此 View 时，出现前面提到的错误。当我调试时，我发现 service.name、service.category 和 service.pricing 中有正确的值

看来我没有正确处理可选值，但我看不出哪里出了问题。

感谢您的帮助。

Answer 1

在可选展开的情况下可能崩溃的行是这一行

    refServices = Database.database().reference().child("Categories");
    refServices.observe(DataEventType.value, with: { (snapshot) in

尝试设置断点并检查 refServices 是否已正确初始化，或者不使用 将 ti 设为可选!

希望这有帮助

诗。请从您的 Swift 代码中删除 ; :P