let str = "{\"names\": [\"Bob\", \"Tim\", \"Tina\"]}"


let data = str.data(using: String.Encoding.utf8, allowLossyConversion: false)!


do {
let json = try JSONSerialization.jsonObject(with: data, options: []) as! [String: AnyObject]
if let names = json["names"] as? [String]
{
print(names)
}
} catch let error as NSError {
print("Failed to load: \(error.localizedDescription)")
}

我建立 快速打字就是为了这个目的。只需粘贴您的示例 JSON 并快速键入就可以为您的 API 数据生成这种类型层次结构:

struct Forecast {
let hourly: Hourly
let daily: Daily
let currently: Currently
let flags: Flags
let longitude: Double
let latitude: Double
let offset: Int
let timezone: String
}


struct Hourly {
let icon: String
let data: [Currently]
let summary: String
}


struct Daily {
let icon: String
let data: [Datum]
let summary: String
}


struct Datum {
let precipIntensityMax: Double
let apparentTemperatureMinTime: Int
let apparentTemperatureLowTime: Int
let apparentTemperatureHighTime: Int
let apparentTemperatureHigh: Double
let apparentTemperatureLow: Double
let apparentTemperatureMaxTime: Int
let apparentTemperatureMax: Double
let apparentTemperatureMin: Double
let icon: String
let dewPoint: Double
let cloudCover: Double
let humidity: Double
let ozone: Double
let moonPhase: Double
let precipIntensity: Double
let temperatureHigh: Double
let pressure: Double
let precipProbability: Double
let precipIntensityMaxTime: Int
let precipType: String?
let sunriseTime: Int
let summary: String
let sunsetTime: Int
let temperatureMax: Double
let time: Int
let temperatureLow: Double
let temperatureHighTime: Int
let temperatureLowTime: Int
let temperatureMin: Double
let temperatureMaxTime: Int
let temperatureMinTime: Int
let uvIndexTime: Int
let windGust: Double
let uvIndex: Int
let windBearing: Int
let windGustTime: Int
let windSpeed: Double
}


struct Currently {
let precipProbability: Double
let humidity: Double
let cloudCover: Double
let apparentTemperature: Double
let dewPoint: Double
let ozone: Double
let icon: String
let precipIntensity: Double
let temperature: Double
let pressure: Double
let precipType: String?
let summary: String
let uvIndex: Int
let windGust: Double
let time: Int
let windBearing: Int
let windSpeed: Double
}


struct Flags {
let sources: [String]
let isdStations: [String]
let units: String
}

它还生成无依赖的封送处理代码，将 JSONSerialization.jsonObject的返回值诱骗到 Forecast中，包括一个方便的构造函数，该构造函数接受一个 JSON 字符串，这样您就可以快速解析一个强类型的 Forecast值并访问它的字段:

let forecast = Forecast.from(json: jsonString)!
print(forecast.daily.data[0].windGustTime)

你可以用 npm i -g quicktype或者 使用网页用户界面从 npm 安装 Quick type 来获得完整的生成代码粘贴到你的操场上。

问题在于 API 交互方法。JSON 解析只在语法上有所改变。主要问题是获取数据的方式。您正在使用的是获取数据的同步方法。不是每个案子都能成功的。您应该使用异步方法来获取数据。通过这种方式，您必须通过 API 请求数据，并等待数据响应。您可以使用 URL 会话和第三方库(如 Alamofire)来实现这一点。下面是 URL Session 方法的代码。

let urlString = "https://api.forecast.io/forecast/apiKey/37.5673776,122.048951"
let url = URL.init(string: urlString)
URLSession.shared.dataTask(with:url!) { (data, response, error) in
guard error == nil else {
print(error)
}
do {
let Data = try JSONSerialization.jsonObject(with: data!) as! [String:Any]
// Note if your data is coming in Array you should be using [Any]()
//Now your data is parsed in Data variable and you can use it normally
let currentConditions = Data["currently"] as! [String:Any]
print(currentConditions)
let currentTemperatureF = currentConditions["temperature"] as! Double
print(currentTemperatureF)
} catch let error as NSError {
print(error)
}
}.resume()

Swift has a powerful type inference. Lets get rid of "if let" or "guard let" boilerplate and force unwraps using functional approach:

1. 这是我们的 JSON。我们可以使用可选的 JSON 或通常的。我在我们的例子中使用可选的:

let json: Dictionary<String, Any>? = ["current": ["temperature": 10]]

2. Helper 函数。我们只需要编写它们一次，然后在任何字典中重用它们:

/// Curry
public func curry<A, B, C>(_ f: @escaping (A, B) -> C) -> (A) -> (B) -> C {
return { a in
{ f(a, $0) }
}
}


/// Function that takes key and optional dictionary and returns optional value
public func extract<Key, Value>(_ key: Key, _ json: Dictionary<Key, Any>?) -> Value? {
return json.flatMap {
cast($0[key])
}
}


/// Function that takes key and return function that takes optional dictionary and returns optional value
public func extract<Key, Value>(_ key: Key) -> (Dictionary<Key, Any>?) -> Value? {
return curry(extract)(key)
}


/// Precedence group for our operator
precedencegroup RightApplyPrecedence {
associativity: right
higherThan: AssignmentPrecedence
lowerThan: TernaryPrecedence
}


/// Apply. g § f § a === g(f(a))
infix operator § : RightApplyPrecedence
public func §<A, B>(_ f: (A) -> B, _ a: A) -> B {
return f(a)
}


/// Wrapper around operator "as".
public func cast<A, B>(_ a: A) -> B? {
return a as? B
}

3. 这就是我们的魔法——提取价值:

let temperature = (extract("temperature") § extract("current") § json) ?? NSNotFound

只有一行代码，没有力量展开或手动类型铸造。这个代码在操场上工作，所以你可以复制和检查它。下面是一个实现 on GitHub.

这是解决你的问题的另一种方法。所以请查看下面的解决方案。希望对你有所帮助。

let str = "{\"names\": [\"Bob\", \"Tim\", \"Tina\"]}"
let data = str.data(using: String.Encoding.utf8, allowLossyConversion: false)!
do {
let json = try JSONSerialization.jsonObject(with: data, options: []) as! [String: AnyObject]
if let names = json["names"] as? [String] {
print(names)
}
} catch let error as NSError {
print("Failed to load: \(error.localizedDescription)")
}

{
"User":[
{
"FirstUser":{
"name":"John"
},
"Information":"XY",
"SecondUser":{
"name":"Tom"
}
}
]
}

如果我使用前面的 json 创建模型 Using this link [blog]: http://www.jsoncafe.com to generate Codable structure or Any Format

模特

import Foundation
struct RootClass : Codable {
let user : [Users]?
enum CodingKeys: String, CodingKey {
case user = "User"
}


init(from decoder: Decoder) throws {
let values = try? decoder.container(keyedBy: CodingKeys.self)
user = try? values?.decodeIfPresent([Users].self, forKey: .user)
}
}


struct Users : Codable {
let firstUser : FirstUser?
let information : String?
let secondUser : SecondUser?
enum CodingKeys: String, CodingKey {
case firstUser = "FirstUser"
case information = "Information"
case secondUser = "SecondUser"
}
init(from decoder: Decoder) throws {
let values = try? decoder.container(keyedBy: CodingKeys.self)
firstUser = try? FirstUser(from: decoder)
information = try? values?.decodeIfPresent(String.self, forKey: .information)
secondUser = try? SecondUser(from: decoder)
}
}
struct SecondUser : Codable {
let name : String?
enum CodingKeys: String, CodingKey {
case name = "name"
}
init(from decoder: Decoder) throws {
let values = try? decoder.container(keyedBy: CodingKeys.self)
name = try? values?.decodeIfPresent(String.self, forKey: .name)
}
}
struct FirstUser : Codable {
let name : String?
enum CodingKeys: String, CodingKey {
case name = "name"
}
init(from decoder: Decoder) throws {
let values = try? decoder.container(keyedBy: CodingKeys.self)
name = try? values?.decodeIfPresent(String.self, forKey: .name)
}
}

解析

    do {
let res = try JSONDecoder().decode(RootClass.self, from: data)
print(res?.user?.first?.firstUser?.name ?? "Yours optional value")
} catch {
print(error)
}

Swift 5 Cant fetch data from your api. 解析 json 最简单的方法是使用 Decodable协议或者 Codable(Encodable & Decodable)。 例如:

let json = """
{
"dueDate": {
"year": 2021,
"month": 2,
"day": 17
}
}
"""


struct WrapperModel: Codable {
var dueDate: DueDate
}


struct DueDate: Codable {
var year: Int
var month: Int
var day: Int
}


let jsonData = Data(json.utf8)


let decoder = JSONDecoder()


do {
let model = try decoder.decode(WrapperModel.self, from: jsonData)
print(model)
} catch {
print(error.localizedDescription)
}