Json iOS playground do 方法中的解析未解析

Question

我正在尝试根据 json 中的标签将一些 json 数据解析为三个不同的数组。我似乎被卡住了，不知道为什么我的 for 循环从未被输入过。我是 iOS 的新手，正在使用它来学习 swift。任何帮助将不胜感激。这是我正在使用的代码：

var myPicture = [String]()
var myPath = [String]()
var mylabel = [String]()


let jsonString = "[{\"picture\" : \"Picture 1 \", \"path\": \"Path 1\" , \"label\" : \"Label 1\"}]"
//Convert jsonString to NSData
let myData = jsonString.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!

do{

let promoJson = try NSJSONSerialization.JSONObjectWithData(myData, options:.AllowFragments)

if let promtions = promoJson[""] as? [[String: AnyObject]] {

    for promtions in promtions {

        if let picture = promtions["picture"] as? String
        {
            myPicture.append(picture)

            if let path = promtions["path"] as? String
            {
                myPath.append(path)

                if let label = promtions["label"] as? String
                {
                    mylabel.append(label)

                }

            }
        }
    }

}

}catch {
print("Error with Json: \(error)")
}
print(myPicture.first)
print(myPath.first)
print(mylabel.first)

打印结果均为零。所以没有任何内容被附加到数组

Answer 1

当你转换的时候它已经是一个数组了。

import Foundation
import UIKit

var myPicture = [String]()
var myPath = [String]()
var mylabel = [String]()


let jsonString = "[{\"picture\" : \"Picture 1 \", \"path\": \"Path 1\" , \"label\" : \"Label 1\"}]"
//Convert jsonString to NSData
let myData = jsonString.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!

do{

    let promoJson = try NSJSONSerialization.JSONObjectWithData(myData, options:.AllowFragments) as! NSArray

        for promtions in promoJson {

            if let picture = promtions["picture"] as? String
            {
                myPicture.append(picture)

                if let path = promtions["path"] as? String
                {
                    myPath.append(path)

                    if let label = promtions["label"] as? String
                    {
                        mylabel.append(label)

                    }

                }
            }

    }

}catch
{
    print("Error with Json: \(error)")
}

print(myPicture.first) // "Optional("Picture 1 ")\n"
print(myPath.first) // "Optional("Path 1")\n"
print(mylabel.first) // "Optional("Label 1")\n"

这样就可以了。

Answer 2

if let promtions = promoJson[""] 部分将不起作用，无论如何也没有用。这只是 promoJson 您必须转换为字典数组。

你离解决方案不远了，看看我的代码工作版本：

do {
    let promoJson = try NSJSONSerialization.JSONObjectWithData(myData, options: [])
    if let promtions = promoJson as? [[String: AnyObject]] {
        for promtion in promtions {
            if let picture = promtion["picture"] as? String {
                myPicture.append(picture)
            }
            if let path = promtion["path"] as? String {
                myPath.append(path)
            }
            if let label = promtion["label"] as? String {
                mylabel.append(label)
            }
        }
    }
} catch let error as NSError {
    print(error.debugDescription)
}

备选

既然问题已解决，让我向您推荐另一种方法：不要为数据使用单独的数组，而是使用一个对象数组来保存数据。

例如，构造这样的结构：

struct Promotion {
    let picture: String
    let path: String
    let label: String
}

以及此结构实例的数组：

var myPromotions = [Promotion]()

现在我们可以解码 JSON，从中创建对象然后将它们存储在数组中：

do {
    let promoJson = try NSJSONSerialization.JSONObjectWithData(myData, options: [])
    if let promtions = promoJson as? [[String: AnyObject]] {
        for promtion in promtions {
            if let picture = promtion["picture"] as? String,
                    path = promtion["path"] as? String,
                    label = promtion["label"] as? String {
                let promo = Promotion(picture: picture, path: path, label: label)
                myPromotions.append(promo)
            }
        }
    }
} catch let error as NSError {
    print(error.debugDescription)
}

现在看看数组的内容，很方便：

for promo in myPromotions {
    print(promo.label)
    print(promo.path)
    print(promo.picture)
}

Json iOS playground do 方法中的解析未解析

Json parsing in iOS playground do method is not parsing

json

ios

swift

swift-playground

xcode7