使用 swift 5 从远程读取 json 内容并在 Xcode 的主界面上打印

Posted 2023-03-16

【中文标题】使用 swift 5 从远程读取 json 内容并在 Xcode 的主界面上打印

【英文标题】：Read json content from remote and printing on main interface in Xcode with swift 5

【发布时间】：2019-08-23 09:09:00

【问题描述】：

从远程 url 读取 json 内容并在 ios 模拟器的主界面上打印时出错。

MBP13"2016 && Mojave 10.14.6 && xcode 10.3(10G8) && swift 5

这是代码示例。我从“https://www.simplifiedios.net/swift-json-tutorial/”做了一点改动

import UIKit

class ViewController: UIViewController 

    //the json file url
    let URL_POSTS = "https://demo.ghost.io/ghost/api/v2/content/posts/?key=22444f78447824223cefc48062";

    //A string array to save all the names
    var nameArray = [String]()

    //the label we create
    @IBOutlet weak var labelTest: UILabel!

    override func viewDidLoad() 
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        //calling the function that will fetch the json
        getJsonFromUrl();
    

    override func didReceiveMemoryWarning() 
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    

    //this function is fetching the json from URL
    func getJsonFromUrl()
        //creating a NSURL
        let url = NSURL(string: URL_POSTS)

        //fetching the data from the url
        URLSession.shared.dataTask(with: (url as URL?)!, completionHandler: (data, response, error) -> Void in

            if let jsonObj = try? JSONSerialization.jsonObject(with: data!, options: .allowFragments) as? NSDictionary 

                //printing the json in console
                print(jsonObj.value(forKey: "posts")!)

                //getting the companies tag array from json and converting it to NSArray
                if let heroeArray = jsonObj.value(forKey: "posts") as? NSArray 
                    //looping through all the elements
                    for heroe in heroeArray

                        //converting the element to a dictionary
                        if let heroeDict = heroe as? NSDictionary 

                            //getting the name from the dictionary
                            if let name = heroeDict.value(forKey: "name") 

                                //adding the name to the array
                                self.nameArray.append((name as? String)!)
                            

                        
                    
                

                OperationQueue.main.addOperation(
                    //calling another function after fetching the json
                    //it will show the names to label
                    self.showNames()
                )
            
        ).resume()
    

    func showNames()
        //looing through all the elements of the array
        for name in nameArray

            //appending the names to label
            labelTest.text = labelTest.text! + name + "\n";
        
            
  

从上面的结果来看，我在从远程 url 获取 json 时在控制台中找到了内容结果似乎没问题，但在 iOS 模拟器的主界面上没有显示任何内容。

json result in console

main interface nothing show up in IOS Simulator

【参考方案1】：

我在使用 JSON 键和 NSDictionary 时遇到了某种问题。对我有用的只是使用 Decodable 协议。我建议使用这个新的 API 进行解析，而不是 JSONSerialization。

这里有一些不错的读物：

https://medium.com/swiftly-swift/swift-4-decodable-beyond-the-basics-990cc48b7375 https://medium.com/xcblog/painless-json-parsing-with-swift-codable-2c0beaeb21c1