iOS Swift JSON解析教程

In this tutorial, we will learn how to parse a JSON response in our iOS Application using Swift. We will display the parsed response in a UITableView. To know more about UITableView, check out this tutorial before proceeding ahead.

在本教程中，我们将学习如何使用Swift在我们的iOS应用程序中解析JSON响应。我们将在UITableView中显示已解析的响应。要了解有关UITableView的更多信息，请先阅读本教程，然后再继续。

Swift JSON解析 (Swift JSON Parsing)

JSON is the most commonly used format to send and receive data from the web services. The data is in the form of key-value pairs. Using Swift Dictionaries we can easily fetch the values from the keys.

JSON是最常用的从Web服务发送和接收数据的格式。数据采用键值对的形式。使用Swift字典，我们可以轻松地从键中获取值。

In this tutorial, we’ll be parsing JSON data from a local resource file.

在本教程中，我们将从本地资源文件中解析JSON数据。

The JSONSerialization class is used to parse a JSON data into a dictionary of key-value pairs by converting the Data object.

JSONSerialization类用于通过转换Data对象将JSON数据解析为键值对字典。

The type of a JSON data is [String: Any].

JSON数据的类型为[String: Any] 。

Let’s create a single view iOS Application in which we’ll parse the data from a locally created JSON file into the TableView.

让我们创建一个单视图iOS应用程序，在其中将本地创建的JSON文件中的数据解析为TableView。

iOS JSON解析示例项目结构 (iOS JSON Parsing Example Project Structure)

In the Main.storyboard we’ve added a label and a TableView to our ViewController.

在Main.storyboard中，我们向ViewController添加了标签和TableView。

We’ve set the TableView delegates to the ViewController.

我们已经将TableView委托设置为ViewController。

For more info on how to set up a TableView using Storyboard, refer this tutorial.

有关如何使用Storyboard设置TableView的更多信息，请参考本教程。

Swift JSON解析代码 (Swift JSON Parsing Code)

We will be parsing JSON data from the file. The response.json file looks like this:

我们将从文件中解析JSON数据。 response.json文件如下所示：

Serialising the data

序列化数据

let url = Bundle.main.url(forResource: "response", withExtension: "json")guard let jsonData = url else{return}
guard let data = try? Data(contentsOf: jsonData) else { return }
guard let json = try? JSONSerialization.jsonObject(with: data, options: []) else{return}

In the above code, we fetch the file over the Bundle.main.url instance.

在上面的代码中，我们通过Bundle.main.url实例获取文件。

The Data instance converts it into a Data format which is then serialized as JSON.

Data实例将其转换为Data格式，然后将其序列化为JSON。

Fetching data from the JSON instance

从JSON实例获取数据

Now that we’ve got the JSON instance, we can fetch the data in the following manner:

现在我们有了JSON实例，我们可以通过以下方式获取数据：

if let dictionary = json as? [String: Any] {if let title = dictionary["title"] as? String {labelHeader.text = title}if let year = dictionary["year"] as? Double {print("Year is \(year)")}if let more_info = dictionary["more_info"] as? Double {//This doesn't get printed.print("More_info is \(more_info)")}for (key, value) in dictionary {print("Key is: \(key) and value is \(value)" )}}

In the TableView, we’ll populate another JSON file :

在TableView中，我们将填充另一个JSON文件：

ViewController.swift

import UIKitclass ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {@IBOutlet weak var labelHeader: UILabel!@IBOutlet weak var tableView: UITableView!var movieList = [MarvelData]()override func viewDidLoad() {super.viewDidLoad()// Do any additional setup after loading the view, typically from a nib.let url = Bundle.main.url(forResource: "response", withExtension: "json")guard let jsonData = urlelse{print("data not found")return}guard let data = try? Data(contentsOf: jsonData) else { return }guard let json = try? JSONSerialization.jsonObject(with: data, options: []) else{return}if let dictionary = json as? [String: Any] {if let title = dictionary["title"] as? String {labelHeader.text = title}if let year = dictionary["year"] as? Double {print("Year is \(year)")}if let more_info = dictionary["more_info"] as? Double {//This doesn't get printed.print("More_info is \(more_info)")}for (key, value) in dictionary {print("Key is: \(key) and value is \(value)" )}}//Now lets populate our TableViewlet newUrl = Bundle.main.url(forResource: "marvel", withExtension: "json")guard let j = newUrlelse{print("data not found")return}guard let d = try? Data(contentsOf: j)else { print("failed")return}guard let rootJSON = try? JSONSerialization.jsonObject(with: d, options: [])else{ print("failedh")return}if let JSON = rootJSON as? [String: Any] {labelHeader.text = JSON["title"] as? Stringguard let jsonArray = JSON["movies"] as? [[String: Any]] else {return}print(jsonArray)let name = jsonArray[0]["name"] as? Stringprint(name ?? "NA")print(jsonArray.last!["year"] as? Int ?? 1970)for json in jsonArray{guard let movieName = json["name"] as? String else{ return }guard let movieYear = json["year"] as? Int else{ return }movieList.append(MarvelData(movieName: movieName, movieYear: movieYear))}self.tableView.reloadData()}}override func didReceiveMemoryWarning() {super.didReceiveMemoryWarning()// Dispose of any resources that can be recreated.}func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {return movieList.count}func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {}func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {let currentMovie = movieList[indexPath.row]let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as UITableViewCellcell.textLabel?.text = currentMovie.movieNamecell.detailTextLabel?.text = "\(currentMovie.movieYear)"return cell}}struct MarvelData {let movieName: Stringlet movieYear: Intpublic init(movieName: String, movieYear: Int) {self.movieName = movieNameself.movieYear = movieYear}
}

In the above code, we’ve parsed the second json file as well and appended each of the JSON Array elements into the array which holds the structures.

在上面的代码中，我们还解析了第二个json文件，并将每个JSON Array元素追加到保存结构的数组中。

To display this data we must call reloadData() over the tableView instance.

要显示此数据，我们必须在tableView实例上调用reloadData() 。

We can make the code that sets the json values in the structure instances much better.

我们可以使在结构实例中设置json值的代码更好。

struct MarvelData {var movieName: Stringvar movieYear: Intinit(_ dictionary: [String: Any]) {self.movieName = dictionary["name"] as? String ?? "NA"self.movieYear = dictionary["year"] as? Int ?? 1970}
}

Doing this we can change our :

这样做我们可以更改：

guard let movieName = json["name"] as? String else{ return }
guard let movieYear = json["year"] as? Int else{ return }
movieList.append(MarvelData(movieName: movieName, movieYear: movieYear))

至

movieList.append(MarvelData(json))

Instead of iterating over the jsonArray using a for loop, we can easily use the handy operator concatMap in Swift. So this:

无需使用for循环遍历jsonArray，我们可以轻松地在Swift中使用方便的运算符concatMap。所以这：

for json in jsonArray
{movieList.append(MarvelData(json))
}

Changes to

更改为

movieList = jsonArray.compactMap{return MarvelData($0)}
//or
movieList = jsonArray.compactMap{MarvelData($0)}
//or
movieList = jsonArray.compactMap(MarvelData.init)

This is the power of Swift!

这就是Swift的力量！

The output of the above application in action is:

上面应用程序的实际输出为：

This brings an end to this tutorial. You can download the project from the link below.

本教程到此结束。您可以从下面的链接下载项目。

iOSJsonParsingiOSJson解析

翻译自: https://www.journaldev.com/21839/ios-swift-json-parsing-tutorial