带有编码器的初始化失败 [英] Failable Initializers with Codable

问题描述

我正在尝试解析以下项数组的json模式，itemID可能不为空。如何使项目nil id itemID 在JSON中不存在？

I'm attempting to parse the following json schema of array of items, itemID may not be empty. How do I make an item nil id itemID does not exist in the JSON?

[{
    "itemID": "123",
    "itemTitle": "Hello"
  },
  {},
  ...
]

我的可解码类如下：

public struct Item: : NSObject, Codable {
    let itemID: String
    let itemTitle: String?
}

private enum CodingKeys: String, CodingKey {
    case itemID
    case itemTitle
}

    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)

        itemID = try container.decode(String.self, forKey: .itemID)
        itemTitle = try container.decodeIfPresent(String.self, forKey: .itemTitle)

        super.init()
    }
}

推荐答案

首先， itemID 是 JSON 响应中的 Int 而不是 String 。因此结构项看起来像

First of all, itemID is an Int and not String in your JSON response. So the struct Item looks like,

public struct Item: Codable {
    let itemID: Int?
    let itemTitle: String?
}

解析 JSON 例如，

if let data = data {
    do {
        let items = try JSONDecoder().decode([Item].self, from: data).filter({$0.itemID == nil})
        print(items)
    } catch {
        print(error)
    }
}

在上面的代码中，您可以简单地过滤器删除 itemID == nil 的项目。

In the above code you can simply filter out the items with itemID == nil.

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