ios - iOS playground do 方法中的 Json 解析不解析

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，正在使用它来快速学习。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)

打印的结果都是零。所以没有任何内容被附加到数组

Answer 1

if let promtions = promoJson[""] 部分将不起作用，而且无论如何也无用。这只是您必须转换为字典数组的 promoJson。

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，让我建议您另一种方法:不要使用单独的数组来存储数据，而是使用一个对象数组来保存数据。

例如，创建这样的结构:

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

以及这个结构实例的数组:

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)
}

现在看数组的内容，很方便:

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