Swift 4解析json为变量 [英] Swift 4 parsing json with variable being the key

问题描述

我想让苹果公司增加新的Codable功能，但我无法解决此问题. 我有一个像这样的json输出

Im trying to get my head around the new Codable feature Apple has added but Im not able to solve this problem. I have a json output which is like this

{
    "Afpak": {
        "id": 1,
        "race": "hybrid",
        "flavors": [
            "Earthy",
            "Chemical",
            "Pine"
        ],
        "effects": {
            "positive": [
                "Relaxed",
                "Hungry",
                "Happy",
                "Sleepy"
            ],
            "negative": [
                "Dizzy"
            ],
            "medical": [
                "Depression",
                "Insomnia",
                "Pain",
                "Stress",
                "Lack of Appetite"
            ]
        }
    }
}

我有一个类似

struct Strain: Codable {
    var name: String
    var id: Int
    var race: String
    var flavors: [String]
    var effects: [String: [String]]

}

因此很明显它将失败，因为我的json中没有名称键.名称应该是"Afpak"，我环顾四周，但是大多数教程都没有给出任何有关如何解决此问题的示例，他们只是做了[String:Strain]，这不是我所需要的.无论如何，有没有将字典的键设置为我的名称变量?

so obviously it will fail because there is no name key inside my json. The name should be "Afpak", I have looked around but most tutorials didnt give any example on how to solve this problem, they just did [String:Strain] which is not what I need. Is there anyway set the key of my dictionary to my name variable?

推荐答案

您可以使用一个小技巧来解决未知的关键问题:为您的Strain结构创建一个辅助结构，使该辅助结构Codable，将响应解码为[String:Helper]，然后创建一个自定义初始化程序，该初始化程序带有2个输入参数，菌株名称和Helper实例.

You can use a small trick to get around the unknown key issue: create a helper struct for your Strain struct, make that helper struct Codable, decode the response as [String:Helper], then create a custom initializer that takes 2 input arguments, the name of the strain and a Helper instance.

通过这种方式，您可以将name存储为Strain的属性，并且不需要复杂的解码即可避免未知的顶级Dictionary密钥的问题.

This way you can store the name as a property of Strain and you won't need an overcomplicated decoding to circumvent the issue of the unknown top level Dictionary key.

struct Strain {
    var name: String
    var id: Int
    var race: String
    var flavors: [String]
    var effects: [String: [String]]

    init(from helper: StrainHelper, with name:String){
        self.name = name
        self.id = helper.id
        self.race = helper.race
        self.flavors = helper.flavors
        self.effects = helper.effects
    }
}

struct StrainHelper: Codable {
    var id: Int
    var race: String
    var flavors: [String]
    var effects: [String: [String]]
}


do {
    let strainHelper = try JSONDecoder().decode([String:StrainHelper].self, from: data)
    guard let strainName = strainHelper.keys.first else {throw NSError(domain: "No key in dictionary",code: 404)}
    let strain = Strain(from: strainHelper[strainName]!, with: strainName)
} catch {
    print(error)
}

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