Swift 4 Codable解码json [英] Swift 4 Codable decoding json

问题描述

我正在尝试实现新的 Codable 协议，所以我在我的结构中添加了 Codable ，但是坚持解码JSON 。

I'm trying to implement the new Codable protocol, so I added Codable to my struct, but am stuck on decoding the JSON.

这是我之前的经历：

结构-

struct Question {
    var title: String
    var answer: Int
    var question: Int
}

客户-

...

guard let data = data else {
    return
}

do {
    self.jsonResponse = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String: Any]
    let questionItems = self.jsonResponse?["themes"] as! [[String: Any]]

    questionItems.forEach {
        let item = Question(title: $0["title"] as! String,
                            answer: $0["answer"] as! Int,
                            question: $0["question"] as! Int)
        questionData.append(item)
    }

} catch {
    print("error")
}

这是我现在拥有的，除了我无法找出解码器部分：

Here's what I have now, except I can't figure out the decoder part:

结构-

struct Question: Codable {
    var title: String
    var answer: Int
    var question: Int
}

客户-

...

let decoder = JSONDecoder()
if let questions = try? decoder.decode([Question].self, from: data) {
    // Can't get past this part
} else {
    print("Not working")
}

它显示无法正常工作，因为我无法通过解码器。解码部分。有任何想法吗？

It prints "Not working" because I can't get past the decoder.decode part. Any ideas? Will post any extra code as needed, thanks!

编辑：

API JSON示例：

Sample of API JSON:

{
  "themes": [
    {
      "answer": 1,
      "question": 44438222,
      "title": "How many letters are in the alphabet?"
    },
    {
      "answer": 0,
      "question": 44438489,
      "title": "This is a random question"
    }
  ]
 }

如果我打印 self .jsonResponse 我得到了：

Optional(["themes": <__NSArrayI 0x6180002478f0>(
{
    "answer" = 7;
    "question" = 7674790;
    title = "This is the title of the question";
},
{
    "answer_" = 2;
    "question" = 23915741;
    title = "This is the title of the question";
}

我的新代码：

struct Theme: Codable {
    var themes : [Question]
}

struct Question: Codable {
    var title: String
    var answer: Int
    var question: Int
}

...

if let decoded = try? JSONDecoder().decode(Theme.self, from: data) {
    print("decoded:", decoded)
} else {
    print("Not working")
}

推荐答案

如果您的JSON具有结构

If your JSON has a structure

{"themes" : [{"title": "Foo", "answer": 1, "question": 2},
             {"title": "Bar", "answer": 3, "question": 4}]}

您需要与 themes 对象等效。添加此结构

you need an equivalent for the themes object. Add this struct

struct Theme : Codable {
    var themes : [Question]
}

现在您可以解码JSON了：

Now you can decode the JSON:

if let decoded = try? JSONDecoder().decode(Theme.self, from: data) {
    print("decoded:", decoded)
} else {
    print("Not working")
}

包含的 Question 对象被隐式解码

这篇关于Swift 4 Codable解码json的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！