Xcode 游乐场 - Swift 4 未接收 JSON 数据

Question

您好，我在 Xcode 游乐场工作，并尝试使用 URLSession 的 API http-get 请求和来自 jsonplaceholder 网站的虚拟数据。

见下面的代码。该代码没有返回错误，但我期待“usableData”中的数据并打印它。数据是：

{ URL: http://jsonplaceholder.typicode.com/users/1 } { 状态代码: 200, Headers {\n "Access-Control-Allow-Credentials" = (\n true\n );\n "CF-Cache-Status" = (\ n HIT\n );\n "CF-RAY" = (\n "445f3d1003761d3e-MEL"\n );\n "缓存控制" = (\n "public, max-age=14400"\n ); \n Connection = (\n "keep-alive"\n );\n "Content-Encoding" = (\n gzip\n );\n "Content-Type" = (\n "application/json; charset= utf-8"\n );\n 日期 = (\n "星期一，2018 年 8 月 6 日 05:52:38 GMT"\n );\n Etag = (\n "W/\"1fd-+2Y3G3w049iSZtw5t1mzSnunngE\" "\n );\n Expires = (\n "Mon, 06 Aug 2018 09:52:38 GMT"\n );\n Pragma = (\n "no-cache"\n );\n Server = ( \n cloudflare\n );\n "Transfer-Encoding" = (\n Identity\n );\n Vary = (\n "Origin, Accept-Encoding"\n );\n Via = (\n "1.1我……”

我期待一些 JSON 格式的数据：

{
    "id": 1,
    "name": "Leanne Graham",
    "username": "Bret",
    "email": "Sincere@april.biz",
    "address": {
        "street": "Kulas Light",
        "suite": "Apt. 556",
        "city": "Gwenborough",
        "zipcode": "92998-3874",
        "geo": {
            "lat": "-37.3159",
            "lng": "81.1496"
        }
    },
    "phone": "1-770-736-8031 x56442",
    "website": "hildegard.org",
    "company": {
        "name": "Romaguera-Crona",
        "catchPhrase": "Multi-layered client-server neural-net",
        "bs": "harness real-time e-markets"
    }
} 

在这个阶段，我只对获取数据感兴趣，而不是对其进行解析。

我做错了什么？欢迎任何帮助。谢谢。

---- 开始代码 ---------------

import PlaygroundSupport
import Foundation
PlaygroundPage.current.needsIndefiniteExecution = true

let urlString = URL(string:"http://jsonplaceholder.typicode.com/users/1")

if let url = urlString {
    let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
        if error != nil {              
            print()
        } else {
            if let usableData = data {
                print(usableData) //JSONSerialization
            }
        }
    }
    task.resume()
}

Answer 1

您的代码很好。如果要查看打印为字符串的 JSON 数据，则需要将字节从 data 转换为字符串：

if let usableData = data {
    let str = String(bytes: data, encoding: .utf8)
    print("\(String(describing: str))") // just for debug output
}

请注意，这不是解析所必需的，您可以按照以下方式进行操作

struct User: Codable {
    let id: Int
    let name, username, email: String
    let address: Address
    let phone, website: String
    let company: Company
}

struct Address: Codable {
    let street, suite, city, zipcode: String
    let geo: Geo
}

struct Geo: Codable {
    let lat, lng: String
}

struct Company: Codable {
    let name, catchPhrase, bs: String
}

if let usableData = data {
    try {
       let user = try JSONDecoder().decode(User.self, from: data)
    } catch {
       print("\(error)"
    }
}

为此

Answer 2

您必须使用 Foundation 类 NSJSONSerialization 将您从 api 获得的 json 数据转换为对象。所以你可以使用下面的行：

let usableData = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: &error) as NSDictionary
print(usableData)