json - json 的 Swift json 动态 key 解析

Question

我有 json 响应，其中只有一个键名更改其余部分是相同的，并且想在不重复相同结构的情况下进行解析。

"attributes": {
  "symbol":"EUR",
  "name":"Euro",
  "precision":2,             
}
    
"attributes":{
  "symbol":"EUR",
  "name":"Euro",
  "precision_for_fiat_price":2,  
}

如何在json解析中动态处理这个precision key

Answer 1

您可以使用自定义 keyDecodingStrategy。

本质上，您编写了一些逻辑来检查当前编码键路径是否符合某些条件，如果符合，则将该键映射到 precision 键。

例如:

struct Root : Codable {
    let attributes: Attributes
}

struct Attributes : Codable {
    let symbol: String
    let name: String
    let precision: Int
    
    enum CodingKeys: CodingKey {
        case symbol
        case name
        case precision
    }
}

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .custom({
    keys in

    // This will decode every precision_for_fiat_price key in the json as "precision".
    // You might not want this. 
    // Make this criteria stricter if you need to. An example is shown below
    if keys.last?.stringValue == "precision_for_fiat_price" {
        return Attributes.CodingKeys.precision
    }

    // this will only decode those precision_for_fiat_price that have "attribute" as their parent as "precision"
//    if stringPath.suffix(2) == ["attributes", "precision_for_fiat_price"] {
//        return Attributes.CodingKeys.precision
//    }
    return keys.last!
})
let json = """
{
    "attributes":{
                  "symbol":"EUR",
                  "name":"Euro",
                  "precision_for_fiat_price":2
                  
     }
}
""".data(using: .utf8)!
let decoded = try decoder.decode(Root.self, from: json)