使用 Codable swift 从文件中解析 JSON

Question

我有包含城市的 JSON 文件

[
{"country":"UA","name":"Hurzuf","_id":707860,"coord":{"lon":34.283333,"lat":44.549999}},
{"country":"RU","name":"Novinki","_id":519188,"coord":{"lon":37.666668,"lat":55.683334}},
{"country":"NP","name":"Gorkhā","_id":1283378,"coord":{"lon":84.633331,"lat":28}},
{"country":"IN","name":"State of Haryāna","_id":1270260,"coord":{"lon":76,"lat":29}},
{"country":"UA","name":"Holubynka","_id":708546,"coord":{"lon":33.900002,"lat":44.599998}},
{"country":"NP","name":"Bāgmatī Zone","_id":1283710,"coord":{"lon":85.416664,"lat":28}},
{"country":"RU","name":"Mar’ina Roshcha","_id":529334,"coord":{"lon":37.611111,"lat":55.796391}},
{"country":"IN","name":"Republic of India","_id":1269750,"coord":{"lon":77,"lat":20}},
{"country":"NP","name":"Kathmandu","_id":1283240,"coord":{"lon":85.316666,"lat":27.716667}},
{"country":"UA","name":"Laspi","_id":703363,"coord":{"lon":33.733334,"lat":44.416668}},
{"country":"VE","name":"Merida","_id":3632308,"coord":{"lon":-71.144997,"lat":8.598333}},
{"country":"RU","name":"Vinogradovo","_id":473537,"coord":{"lon":38.545555,"lat":55.423332}},
{"country":"IQ","name":"Qarah Gawl al ‘Ulyā","_id":384848,"coord":{"lon":45.6325,"lat":35.353889}},
{"country":"RU","name":"Cherkizovo","_id":569143,"coord":{"lon":37.728889,"lat":55.800835}},
{"country":"UA","name":"Alupka","_id":713514,"coord":{"lon":34.049999,"lat":44.416668}},
{"country":"DE","name":"Lichtenrade","_id":2878044,"coord":{"lon":13.40637,"lat":52.398441}},
{"country":"RU","name":"Zavety Il’icha","_id":464176,"coord":{"lon":37.849998,"lat":56.049999}},
{"country":"IL","name":"‘Azriqam","_id":295582,"coord":{"lon":34.700001,"lat":31.75}},
{"country":"IN","name":"Ghūra","_id":1271231,"coord":{"lon":79.883331,"lat":24.766666}}
]

这些只是少数条目，我的文件中有近 1000 个条目。 我需要应用分页来加载 100 个条目。

我创建了

codable

如下

struct Cities: Codable {
    let city: [City]?
    let pagination: Pagination?
}

struct City: Codable{
    let country : String
    let name : String
    let _id : Int
    let coord: [Coordinates]?
}

struct Coordinates: Codable {
    let lat : Double?
    let lon : Double?
}

struct Pagination: Codable {
    let limit, offset: Int?
}

我的解析方法是这样的，

func getDataFrom(completion: @escaping (Cities?, Error?) -> Void) {
        let url = Bundle.main.url(forResource: "cities", withExtension: "json")!
        let data = try! Data(contentsOf: url)
        do {
            let jsonDescription = try JSONDecoder().decode(Cities.self, from: data)
            print(jsonDescription)
            completion(jsonDescription,nil)
        }
        catch let jsonError {
            print("Json Error:", jsonError)
        }
    }

当我解析数据时，它会进入 catch 块并给出此错误

Json Error: typeMismatch(Swift.Dictionary<Swift.String, Any>, Swift.DecodingError.Context(codingPath: [], debugDescription: "Expected to decode Dictionary<String, Any> but found an array instead.", underlyingError: nil))

谁能告诉我我做错了什么。 我需要解析这些数据并在表格视图上显示分页。

提前致谢。

Answer 1

您正在尝试解码

Cities.self

的类型，但您的 JSON 是一个数组 - 它以“[”开头并以“]”结尾。您可能想尝试在解码器调用中声明类型

[Cities].self

。

let jsonDescription = try JSONDecoder().decode([City].self, from: data)

编辑：

@Joakim_Danielson 发现了一个问题，您需要解码数组

[City]

而不是

[Cities]

，因为这就是您的 JSON（我相应地编辑了上面的代码行）。

但是还有另一个问题：结构体

coord

中的属性

City

被声明为数组

[Coordinates]?

，但是您的 JSON 在“coord”键中没有数组 - 只是一个实例。

尝试更改您的

coord

属性，使其成为

Coordinate?

的类型。

Answer 2

结构产品：可编码{ 让产品：[产品]？ 让总计、跳过、限制：Int？ }

结构产品：可编码{ 让 id: Int? 让标题，描述：字符串？ 出租价格： Int？ 让折扣百分比，评级：双倍？ 让股票：Int？ 让品牌，类别：字符串？ 让缩略图：字符串？ 让图像：[字符串]？ }

类 HttpsHandler{ func getApiData（url：URL，requestType：T.Type，completionHandler：@escaping（_结果：T？）-> Void）{ URLSession.shared.dataTask(with: url) { data, URLResponse, 错误 做{ let result = try JSONDecoder().decode(T.self, from: data!) 完成处理程序（结果） }抓住{ print("解码 json 时出错") } }。恢复（） } }

类产品类{ 让 _httpsHandler: HttpsHandler

init(_httpsHandler: HttpsHandler) {
    self._httpsHandler = _httpsHandler
}
func getProductData() -> Void{
    _httpsHandler.getApiData(url: URL(string: urlProduct)!, requestType: Products.self) { result in
        if let productsResult = result{
            if let products = productsResult.products{
                for produts in products {
                    print(produts.title ?? "")
                }
            }
        }
    }
}

}

让产品 = ProductClass(_httpsHandler: HttpsHandler()) 产品.getProductData()