将JSON解码为Swift模型而不是根级别

单独使用jsondecoder,没有某种外部结构就无法解码,因为您的结果将是 数组 属于外部实体的第条。因此,仅仅定义一个物品永远是不够的。

如果您不喜欢声明一个外部结构,您不需要为任何其他目的而进行深入到 "articles" 密钥,只需声明即可轻松解决 暂时地 在有限的范围内进行深入到 “文章” 关键。因此,程序的其余部分保留了项目结构,但外部结构不存在。

例如:

struct Article: Decodable {
    // ... your code here ...
}
func getArticles(_ d:Data) -> [Article] {
    struct Articles: Decodable { // this struct is temporary
        let articles:[Article]
    }
    return try! JSONDecoder().decode(Articles.self, from: d).articles
}

其他代码现在可以看到项目结构并可以调用 getArticles 解析JSON并接收项目数组,但是其他代码永远不知道(也永远不知道)额外的项目结构存在;它只在 获得文章 作为一种局部函数。它并不比在函数体中临时创建的任何其他局部变量更令人反感。

你可以尝试结合 JSONSerialization 具有 JSONDecoder

do
{
    let tr = try JSONSerialization.jsonObject(with:data, options:[]) as! [String:Any] 
    guard let content =  tr["articles"] else { return }
    let articlesData = try JSONSerialization.data(withJSONObject:content, options: [])
    let res = try JSONDecoder().decode([Article].self, from: articlesData) 
    print(res) 
}
catch 
{
    print(error)
}

考虑重组数据。您需要构造数据模型以匹配JSON数据的数据结构。只能包含所需内容,但必须包含要访问的属性的每个父级或级别。以维基百科API的以下示例为例。它打印出JSON数据结构中三个层次的标题属性。它遗漏了几个属性,正如您可以从JSON示例代码中看到的那样,但是它包含了访问我想要的属性所需的每个父级。

import UIKit

struct Item: Decodable {
    var title: String
}

struct Search: Decodable {
    var search: [Item]
}

struct Result: Decodable {
    var query: Search
}

func getSearchResults(){
    let url = URL(string: "https://en.wikipedia.org/w/api.php?action=query&list=search&srsearch=swift%204&utf8=&format=json")!

    URLSession.shared.dataTask(with: url) { (data, response, error) in
    if let urlResponse = response as? HTTPURLResponse, urlResponse.statusCode == 200 {
        guard let data = data else { return }
        do {
            let results = try JSONDecoder().decode(Result.self, from: data)
            for item in results.query.search {
                print(item.title)
            }
        } catch let error as NSError {
            print("error: \(error)")
        }
    }
}.resume()
}
getSearchResults()

JSON示例:

{
"batchcomplete": "",
"continue": {
    "sroffset": 10,
    "continue": "-||"
},
"query": {
    "searchinfo": {
        "totalhits": 30349
    },
    "search": [
        {
            "ns": 0,
            "title": "Swift",
            "pageid": 219023,
            "size": 13896,
            "wordcount": 1496,
            "snippet": "The <span class=\"searchmatch\">swifts</span> are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows, but are not closely related to any passerine species",
            "timestamp": "2018-12-28T21:29:44Z"
        },
        {
            "ns": 0,
            "title": "Swift (programming language)",
            "pageid": 42946389,
            "size": 49365,
            "wordcount": 5244,
            "snippet": "2015. <span class=\"searchmatch\">Swift</span> 3.0 was released on September 13, 2016. <span class=\"searchmatch\">Swift</span> <span class=\"searchmatch\">4</span>.0 was released on September 19, 2017. <span class=\"searchmatch\">Swift</span> <span class=\"searchmatch\">4</span>.1 was released on March 29, 2018. <span class=\"searchmatch\">Swift</span> won first",
            "timestamp": "2018-12-19T02:52:33Z"
        },
        {
            "ns": 0,
            "title": "Taylor Swift",
            "pageid": 5422144,
            "size": 237225,
            "wordcount": 18505,
            "snippet": "Taylor Alison <span class=\"searchmatch\">Swift</span> (born December 13, 1989) is an American singer-songwriter. One of the world's leading contemporary recording artists, she is known",
            "timestamp": "2018-12-26T21:55:51Z"
        },

这是打印输出:

//Swift
//Swift (programming language)
//Taylor Swift