[英]How to extract a key value pair from a nested dictionary and output it in json
[英]How parse a json data that has a dictionary key:value pair? I'm trying to extract the symbol and value pair
如何正確解析以下json數據? 我的問題是: if let rates = data["rates"] as? NSDictionary...
if let rates = data["rates"] as? NSDictionary...
json數據
{ "valid": true,
"timestamp": 1579683079,
"base": "USD",
"rates": {
"AED": 3.67316,
"AFN": 77.99911,
"ALL": 110.11741,
...
"ZAR": 14.45,
"ZMW": 14.63257
}
}
代碼
import UIKit
struct CurrencyRate {
var valid: String
var timestamp: Int
var base: String
var rates: [String:Double] = [:]
}
class ViewController: UIViewController {
var mySymbols:[String] = []
var myValues:[Double] = []
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
let jsonUrlString = "https://currencyapi.net/api/v1/rates?key=6b171cc58787d922eb53e3684d97784d165a&base=USD"
guard let url = URL(string: jsonUrlString) else { return }
URLSession.shared.dataTask(with: url) { (data, response, err) in
guard let data = data else { return }
//let dataAsString = String(data: data, encoding: .utf8)
if let rates = data["rates"] as? NSDictionary {
for (key, value) in rates {
self.mySymbols.append((key as? String)!)
self.myValues.append((value as? Double)!)
}
}
}.resume()
}
}
語法
for (key, value) in ...
枚舉字典僅適用於本機 Swift 字典。
這應該可以工作,如果您轉換為特定的[String:Double]
您甚至可以擺脫key
和value
的丑陋類型轉換。
if let rates = data["rates"] as? [String:Double] {
for (key, value) in rates {
self.mySymbols.append(key)
self.myValues.append(value)
}
}
但是,我們鼓勵您使用可Decodable
協議來解析 JSON。 只有一些細微的變化。
struct CurrencyRate : Decodable {
let valid: Bool // must be Bool
let timestamp: Date
let base: String
let rates: [String:Double]
}
var rates = [String:Double]()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
let jsonUrlString = "https://currencyapi.net/api/v1/rates?key=6b171cc58787d922eb53e3684d97784d165a&base=USD"
guard let url = URL(string: jsonUrlString) else { return }
URLSession.shared.dataTask(with: url) { (data, _, error) in
guard let error = error else { print(error); return }
do {
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .secondsSince1970
let result = try decoder.decode(CurrencyRate.self, from: data!)
self.rates = result.rates
print(rates)
} catch {
print(error)
}
}.resume()
}
timestamp
被解碼為Date
不要使用NSDictionary
- 在 Swift 中使用Dictionary
類型。 此外,你有data
,它根本不是字典。 它是Data
類型。 使用應該將您的數據轉換為您的類型。 嘗試使用此代碼:
URLSession.shared.dataTask(with: url) { (data, response, err) in
guard let data = data else { return }
let jsonResult = try? JSONSerialization.jsonObject(with: data)
if let dict = jsonResult as? Dictionary<String, Any>, let rates = dict["rates"] as? Dictionary<String, Double> {
for (key, value) in rates {
print(key, value)
self.mySymbols.append(key)
self.myValues.append(value)
}
}
}.resume()
Codable
有一種方法,但我想這將是您的下一個挑戰。 另外請記住,代碼是異步執行的,全局變量中的數據不會立即出現
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.