时间戳

首页 > 解决方案 > 如何为动态键、json解析、swift5创建模型

ios - 如何为动态键、json解析、swift5创建模型

问题描述

我正在解析 json 数据并尝试创建一个模型，但无法弄清楚如何实现标题并从 json 数据（我提供的）中提取属性，因为pageids属性是动态的。请告诉我如何创建模型以title使用 id 从页面中提取属性（存储在pageids属性中）

jsonData 链接https://en.wikipedia.org/w/api.php?exintro=&titles=canterbury%20bells&indexpageids=&format=json&pithumbsize=500&explaintext=&redirects=1&action=query&prop=extracts%7Cpageimages

我尝试了一下，下面是我的代码，但我认为这不正确

var ID = ""
struct Document:Codable {
    
    let batchcomplete:String
    let query:Query
}
struct Query:Codable {
    let normalized:[Normalized]
    
    let pages:Pages
    
    var pageids:[String]{
        didSet{
            ID = oldValue[0]
        }
    }
    
}

struct Normalized:Codable {
    let from:String
    let to:String // it is a name of an flower
}
struct Pages:Codable {
    let id:[Pages2]
    enum CodingKeys:CodingKey {
        case id = "\(ID)"
    }
}
struct Pages2:Codable {
    let title:String // this is an official name of flower
    let extract:String // this is a body
    let thumbnail:Thumbnail
}
struct Thumbnail:Codable {
    let source:String //this is an url for photo
}

标签： iosjsonswiftxcodecodable

解决方案

映射 JSON 的模型将如下所示：

struct Document: Codable {
    let batchcomplete: String
    let query: Query
}

struct Query: Codable {
    let normalized: [Normalized]
    var pageids: [String]
    let pages: [String: Page]
}

struct Normalized: Codable {
    let from: String
    let to: String
}

struct Page: Codable {
    let title: String
    let extract: String
    let thumbnail: Thumbnail
}
struct Thumbnail: Codable {
    let source: String
}

pageids并且您可以使用数组和pages字典访问每个页面：

let decoder = JSONDecoder()
do {
    let decoded = try decoder.decode(Document.self, from: Data(jsonString.utf8))
    decoded.query.pageids.forEach { id in
        guard let page = decoded.query.pages[id] else { return }
        print(page.title)
    }
} catch {
    print(error)
}

但是，我更愿意对模型进行一些小改动，以便更轻松地访问页面。这将需要自定义实现Query结构的解码：

struct Query: Decodable {
    let normalized: [Normalized]
    let pages: [Page]
    
    enum CodingKeys: String, CodingKey {
        case normalized
        case pageids
        case pages
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        normalized = try container.decode([Normalized].self, forKey: .normalized)
        
        let pageids = try container.decode([String].self, forKey: .pageids)
        let pagesDict = try container.decode([String: Page].self, forKey: .pages)
        pages = pageids.compactMap { pagesDict[$0] }
    }
}

然后，访问每个页面就像循环一样简单：

let decoder = JSONDecoder()
do {
    let decoded = try decoder.decode(Document.self, from: Data(jsonString.utf8))
    decoded.query.pages.forEach { page in
        print(page.title)
    }
} catch {
    print(error)
}

推荐阅读