为什么无法在 Swift Project 中访问我的模型类？

Question

如何从 ViewController 访问我的模型并使用模型数据加载到表格视图中？？？？

源码Link

我的 ViewController 是这样的

import UIKit

class ViewController: UIViewController {
    var cclm: CountryCodeListModel?

    override func viewDidLoad() {
        super.viewDidLoad()
        Timer.scheduledTimer(timeInterval: 3, target: self, selector: #selector(hello), userInfo: nil, repeats: true)
        readLocalJSONFile(forName: "countryList")

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

    override func viewDidAppear(_ animated: Bool) {
        
    }
    
    @objc func hello()
     {
        print(cclm?.data?[0].flag)
     }

}

我的模型类看起来像这样

struct CountryCodeList : Decodable {
    var alpha2Code: String?
    var alpha3Code: String?
    var flag      : String?
    var name      : String?
    var code      : String?
}

public struct CountryCodeListModel : Decodable {
    var data      : [CountryCodeList]?
}

var cclm: CountryCodeListModel?


//Method to load json

func readLocalJSONFile(forName name: String) {
    do {
        if let filePath = Bundle.main.path(forResource: name, ofType: "json") {
            let fileUrl = URL(fileURLWithPath: filePath)
            let data = try Data(contentsOf: fileUrl)
            if let countryCodeObject = parse(jsonData: data) {
                cclm = countryCodeObject
                print(cclm?.data?[1].alpha2Code ?? "")  //Printing Correct Value
            }
        }
    } catch {
        print("error: \(error)")
    }
}



func parse(jsonData: Data) -> CountryCodeListModel?{
    var dataArray : [Dictionary<String,Any>] = [[:]]
    var country = Dictionary<String,Any>()
    var modelData = Dictionary<String,Any>()
    do {
        // make sure this JSON is in the format we expect
        if let json = try JSONSerialization.jsonObject(with: jsonData, options: []) as? Dictionary<String,Any> {
            dataArray.removeAll()
            for item  in json["data"] as! [Dictionary<String, Any>] {
                country = item
                
                let url = URL(string: country["flag"] as? String ?? "")
                let data = try? Data(contentsOf: url!) //make sure your image in this url does exist, otherwise unwrap in a if let check / try-catch
                let image = UIImage(data: data!)
                let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
                let fileName = url?.lastPathComponent // name of the image to be saved
                let fileURL = documentsDirectory.appendingPathComponent(fileName ?? "")
                if let data = image?.jpegData(compressionQuality: 1.0){
                    do {
                        try data.write(to: fileURL)
                        country["flag"] = fileURL.absoluteString
                        //print("file saved")
                        //urlAsString = fileURL.absoluteString
                    } catch {
                        print("error saving file:", error)
                    }
                }
                
                dataArray.append(country)
                country.removeAll()
                
                    
                
            }
            modelData["data"] = dataArray
            //print(modelData)
            let jsonData1 = try JSONSerialization.data(withJSONObject: modelData, options: [])
            
            do {
                    let decodedData = try JSONDecoder().decode(CountryCodeListModel.self, from: jsonData1)
                
                    return decodedData
                } catch {
                    print("error: \(error)")
                }
            
        }
    } catch let error as NSError {
        print("Failed to load: \(error.localizedDescription)")
    }
    return nil
}

问题陈述：

我正在读取本地json并获取flag key的url值并将相应的图像下载到本地。下载后，我将获取本地路径并在字典中更新，然后创建 JSON 对象并更新我的模型类。

现在，我正在尝试从 ViewController 访问我的模型类，如下所示

print(CountryCodeListModel?.data?[0].name) //check screenshot for error
 print(cclm?.data?[0].flag)                 // this prints nil always

请检查附上的错误截图2

我的 JSON 看起来像这样

{
   "meta":{
      "success":true,
      "message":"Successfully retrieved country details",
      "code":"200"
   },
   "data":[
      {
         "alpha2Code":"AF",
         "alpha3Code":"AFG",
         "flag":"https://raw.githubusercontent.com/DevTides/countries/master/afg.png",
         "name":"Afghanistan",
         "code":"+93"
      },
      {
         "alpha2Code":"AX",
         "alpha3Code":"ALA",
         "flag":"https://raw.githubusercontent.com/DevTides/countries/master/ala.png",
         "name":"Aland Islands",
         "code":"+358"
      },
      {
         "alpha2Code":"AL",
         "alpha3Code":"ALB",
         "flag":"https://raw.githubusercontent.com/DevTides/countries/master/alb.png",
         "name":"Albania",
         "code":"+355"
      },
      {
         "alpha2Code":"DZ",
         "alpha3Code":"DZA",
         "flag":"https://raw.githubusercontent.com/DevTides/countries/master/dza.png",
         "name":"Algeria",
         "code":"+213"
      },
      {
         "alpha2Code":"AS",
         "alpha3Code":"ASM",
         "flag":"https://raw.githubusercontent.com/DevTides/countries/master/asm.png",
         "name":"American Samoa",
         "code":"+1684"
      }
]
}

Answer 1

您正在尝试解码不存在的内容。

print(CountryCodeListModel?.data?[0].name) //check screenshot for error
 print(cclm?.data?[0].flag)                 // this prints nil always

上面的代码说明了你想要的：

1. 的名字
2. 位置0的可变数据
3. 结构CountryCodeListModel。

你想做的是：

1. 的名字
2. 位置 0 的变量
3. CountryCodeListModel 结构的实例。

例如...

func readLocalJSONFile(forName name: String) {
    do {
        if let filePath = Bundle.main.path(forResource: name, ofType: "json") {
            let fileUrl = URL(fileURLWithPath: filePath)
            let data = try Data(contentsOf: fileUrl)
            if let countryCodeObject = parse(jsonData: data) {
                cclm = countryCodeObject
                print(cclm?.data?[1].alpha2Code ?? "")  //Printing Correct Value
                print(cclm?.data?[0].flag ?? "")
                print(countryCodeObject?.data[0].flag ?? "") // Same as the line above
            }
        }
    } catch {
        print("error: \(error)")
    }
}

除非您尝试使用static 变量（您将使用CountryCodeListModel.data），否则您需要确保您实际使用的是结构的实例或类的对象来引用您的属性。

警告

CountryCodeListModel 是一个结构。 CountryCodeListModel() 是结构 CountryCodeListModel 的一个实例。由于您可以拥有结构的多个实例，因此在访问数据时需要引用特定的结构。因此，CountryCodeListModel.data 将不起作用，它必须是CountryCodeListModel().data。在这种情况下，您拥有cclm.data。