我如何使用 Alamofire 和 Swift Decode 从 JSON 解码和访问 Double

Question

I try do decode and access specific exchange rate for specific currency using Alamofire and Swift decode:

this is my model:

    struct Listek: Codable {
    let base: String
    let date: String
    let rates: [String: Double]

    enum CodingKeys: String, CodingKey {
        case base = "base"
        case date = "date"
        case rates = "rates"
    }
}

this is Alamofire API call + decode

let apiToContact = "https://api.exchangeratesapi.io/latest"
    AF.request(apiToContact).responseJSON { (response) in
    print(response)
    guard let data = response.data else { return }
    do {
    let st = try JSONDecoder().decode(Listek.self, from: data)
        print (st.rates)
        print (st.base)
        print (st.date)

    }
    catch {
    print("error")
    }

So far so good, but I fail in accessing the single currency and its rate value. I would like declare a variable "JPYrate" with value of JPY rate from JSON. Can you please navigate me?

Answer 1

You can simply get the value corresponding to key JPY from rates Dictionary like so,

let JPYrate = st.rates["JPY"]

Also, there is no need to create enum CodingKeys , if the key names are same as the property names. So, your struct Listek looks like,

struct Listek: Codable {
    let base: String
    let date: String
    let rates: [String:Double]
}

Answer 2

exchangeratesapi seems to send consistent data. if so my suggestion is to decode the rates into a dedicated struct

struct Listek: Decodable {
    let base: String
    let date: String
    let rates: Rates
}

struct Rates: Decodable {
    let CAD, HKD, ISK, PHP, DKK, HUF, CZK, AUD, RON, SEK, IDR, INR, BRL, RUB, HRK, JPY, THB, CHF, SGD, PLN, BGN, TRY, CNY, NOK, NZD, ZAR, USD, MXN, ILS, GBP, KRW, MYR : Double
}

Then you can get the rate directly

print(st.rates.JPY)

Answer 3

First, you can make a computed property to access the JPY rate:

var jpyRate: Double? { rates["JPY"] }

Or parse the rates into a specific type as recommended by @vadian.

Second, you can use Alamofire's responseDecodable method to do the decoding automatically.

AF.request(apiToContact).responseDecodable(of: Listek.self) { response in
    debugPrint(response)
}