Swift 4解析json为变量

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?

答

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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