在 swift 中努力 JSON 解析

Question

我正在尝试将 JSON 格式的数据从我的服务器加载到 IOS 应用程序中。

这是我的 JSON:

[
  {
    "BankName": "bank1",
    "CurrencyName": "cur1",
    "SellRate": "0.65",
    "BuyRate": "0.55",
    "OfficialRate": "0.6"
  },
  {
    "BankName": "bank1",
    "CurrencyName": "cur2",
    "SellRate": "1.65",
    "BuyRate": "1.55",
    "OfficialRate": "1.6"
  }
]

我的项目中有2个文件：

1:

import Foundation
class Shot {
    var bankName: String!
    var currencyName: String!
    var sellRate: String!
    var buyRate: String!
    var offRate: String!

    init (data: NSDictionary) {          
        self.bankName = getStringFromJSON(data, key:"BankName")
        self.currencyName = getStringFromJSON(data, key:"CurrencyName")
        self.sellRate = getStringFromJSON(data, key:"SellRate")
        self.buyRate = getStringFromJSON(data, key:"BuyRate")
        self.offRate = getStringFromJSON(data, key: "OfficialRate")
    }

    func getStringFromJSON(data: NSDictionary, key: String) -> String {                    
        if let info = data[key] as? String{
            return info
        }
        return ""
    }
}

2:

import Foundation
class JsonTest {    
    func loadJson(completion: ((AnyObject) -> Void)!) {    
        var urlString = "http://a.com/g.php"        
        let session = NSURLSession.sharedSession()
        let sourceUrl = NSURL(string: urlString)

        var task = session.dataTaskWithURL(sourceUrl!){
            (data, response, error) -> Void in

            if error != nil {
               println(error.localizedDescription)
            } else {

                var error: NSError?
                var jsonData = NSJSONSerialization.JSONObjectWithData(data, options: .MutableContainers, error: &error) as NSArray

                var shots = [Shot]()

                println(jsonData)

                for shot in jsonData{
                    let shot = Shot(data: shot as NSDictionary)
                    shots.append(shot)                    
                }                
                println(shots)   //[jsontest.Shot, jsontest.Shot]                
            }
        }        
        task.resume()
    }
}

我正在尝试在我的应用程序启动时自动填充数组。为此，我在 mainViewController class.

中有一个代码

override func viewDidLoad() {
    super.viewDidLoad()

   let api = JsonTest()
    api.loadJson(nil)

}

当我尝试在第二个文件中打印 shots 变量时出现问题。它 returns [jsontest.Shot, jsontest.Shot] 当我期待字典数组时。

println(jsonData) 工作正常并显示来自 URL.

的 JSON 数据

任何人都可以告诉我程序中有什么问题吗？

Answer 1

"shots" 是 Shot 实例的数组，不是字典：

class Shot {
    var bankName: String!
    var currencyName: String!
    var sellRate: String!
    var buyRate: String!
    var offRate: String!

    init (data: NSDictionary) {
        self.bankName = getStringFromJSON(data, key:"BankName")
        self.currencyName = getStringFromJSON(data, key:"CurrencyName")
        self.sellRate = getStringFromJSON(data, key:"SellRate")
        self.buyRate = getStringFromJSON(data, key:"BuyRate")
        self.offRate = getStringFromJSON(data, key: "OfficialRate")
    }

    func getStringFromJSON(data: NSDictionary, key: String) -> String {
        if let info = data[key] as? String{
            return info
        }
        return ""
    }
}

var shots = [Shot]()
let urlString = "http://almazini.lt/getrates.php"
let sourceUrl = NSURL(string: urlString)
// Using NSData instead of NSURLSession for experimenting in Playground
let data = NSData(contentsOfURL: sourceUrl!)
var error: NSError?
// As I'm using Swift 1.2 I had to change "as" with "as!"
let jsonData = NSJSONSerialization.JSONObjectWithData(data!, options: .MutableContainers, error: &error) as! NSArray
for shot in jsonData{
    let shot = Shot(data: shot as! NSDictionary)
    shots.append(shot)
}
println(shots[0].bankName)

更新 Swift 2

var shots = [Shot]()
let urlString = "http://almazini.lt/getrates.php"
// Using NSData instead of NSURLSession for experimenting in Playground
if let sourceUrl = NSURL(string: urlString) {
    NSURLSession.sharedSession().dataTaskWithURL(sourceUrl, completionHandler: { (data, response, error) in
        if error == nil {
            if let data = data, jsonData = try? NSJSONSerialization.JSONObjectWithData(data, options: []), jsonArray = jsonData as? [NSDictionary] {
                for item in jsonArray {
                    let shot = Shot(data: item)
                    shots.append(shot)
                }
                print(shots[0].bankName)
            } else {
                print("no JSON data")
            }
        } else {
            print(error!.localizedDescription)
        }
    }).resume()
}

Answer 2

好像有两个问题：

您正在尝试使用 println 进行调试，而不是设置断点并检查您的对象值。
您还没有为您的对象创建 description 或 debugDescription 属性，因此您的对象上的 println 只是使用一些默认实现。

shots 是自定义对象的数组，因此当您调用 println 时，它使用 description 作为 Array，打印出数组，逗号分隔，在方括号内。

Swift 中 classes 的默认 description 属性仅打印 class 名称。

理想情况下，您应该只使用断点来检查对象的值以确定它是否正确初始化，但如果让它们正确打印真的很重要，那么只需要实现 description 属性:

override var description: String {
    get {
        // build and return some string that represents your Shot object
    } 
}

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