Swift JSONDecoder 在构建期间抛出错误

Question

你好，我有一个像这样的 json 文件

}
"CYYZ": {
        "icao": "CYYZ",
        "iata": "YYZ",
        "name": "Lester B. Pearson International Airport",
        "city": "Toronto",
        "state": "Ontario",
        "country": "CA",
        "elevation": 569,
        "latitude": 43.6772003174,
        "longitude": -79.6305999756,
        "tz": "America\/Toronto"
    },
    "CYZD": {
        "icao": "CYZD",
        "iata": "YZD",
        "name": "Downsview Airport",
        "city": "Toronto",
        "state": "Ontario",
        "country": "CA",
        "elevation": 652,
        "latitude": 43.7425003052,
        "longitude": -79.4655990601,
        "tz": "America\/Toronto"
    },
    "CYZE": {
        "icao": "CYZE",
        "iata": "YZE",
        "name": "Gore Bay Manitoulin Airport",
        "city": "Gore Bay",
        "state": "Ontario",
        "country": "CA",
        "elevation": 635,
        "latitude": 45.8852996826,
        "longitude": -82.5678024292,
        "tz": "America\/Toronto"
    }
}

我做了一个这样的结构

struct AirportData: Codable{
    let iata: String
    let name: String
    let longitude: Double
    let latitude: Double
}

我编写了以下代码来设置 url 并使其成为字符串，然后我用它来解码 json

    override func viewDidLoad() {
            super.viewDidLoad()

//make url for file path
    guard let jsonURL = Bundle(for: type(of: self)).path(forResource: "airports", ofType: "json") else {
                return
            }
            //make url a string
            guard let jsonString = try? String(contentsOf: URL(fileURLWithPath:jsonURL), encoding: String.Encoding.utf8) else {
                return
            }
            
            var airports: AirportData?
            do{
                airports = try JSONDecoder().decode(AirportData.self, from: Data(jsonString.utf8))
            }
            catch{
                print("error occured when decoding")
            }
            
            
            guard let results = airports else {
                return
            }
            
            print(results.iata)
                
            }

我不断收到“解码时出错”

请帮助我遵循this 教程，但没有得到相同的结果，也许我的结构是错误的。谢谢。

Answer 1

首先你的json不正确，第一个括号应该是“{”而不是“}”。

第二，你的数据结构不正确，用这个：

struct AirportData: Codable {
    let icao, iata, name, city: String
    let state, country: String
    let elevation: Int
    let latitude, longitude: Double
    let tz: String
}

typealias Response = [String: AirportData] 

第三，你的viewDidLoad 代码是一团糟。使用类似这样的方法来获取您的数据：

override func viewDidLoad() {
    super.viewDidLoad()
    var airports: [String:AirportData]?
    if let url = Bundle.main.url(forResource: "airports", withExtension: "json") {
        do {
            let data = try Data(contentsOf: url)
            airports = try JSONDecoder().decode(Response.self, from: data)
            print("\n---> airports: \(airports) \n")
        } catch {
            print("error occured when decoding: \(error)")
        }
    }
}