JSON decodable swift 4 - json

Question

I'm having a terrible time creating a public struct for the following JSON. I'm trying to extract the temp and humidity. I've tried to to extract the following JSON but I think I'm having a problem with way I'm identifying each of the variables.
Here's the JSON:
{"coord":{"lon":-82.26,"lat":27.76},"weather":[{"id":804,"main":"Clouds","description":"overcast clouds","icon":"04n"}],"base":"stations","main":{"temp":66.24,"pressure":1021,"humidity":63,"temp_min":62.6,"temp_max":69.8},"visibility":16093,"wind":{"speed":8.05,"deg":80},"clouds":{"all":90},"dt":1523500500,"sys":{"type":1,"id":726,"message":0.0051,"country":"US","sunrise":1523531237,"sunset":1523577156},"id":420006939,"name":"Brandon","cod":200}
And here's the struct
public struct Page: Decodable {
private enum CodingKeys : String, CodingKey {
case coord = "coord", weather = "weather", mainz = "main", visibility = "visibility", wind = "wind", clouds = "clouds", dt = "dt", sys = "sys", id = "id", name = "name", cod = "cod"}
let coord: String
let weather: [String]
let mainz: String
let visibility: Int
let wind: String
let clouds: String
let dt: Int
let sys: String
let id: Int
let name: String
let cod: Int
public struct Main: Decodable {
private enum CodingKeys : String, CodingKey {
case temp = "temp", pressure = "pressure",humidity = "humidity", temp_min = "temp_min", temp_max = "temp_max"
}
let temp: Int
let pressure: Int
let humidity: Int
let temp_min: Int
let temp_max: Int
}
...and the code I'm using the decode...
// Make the POST call and handle it in a completion handler
let task = session.dataTask(with: components.url!, completionHandler: {(data, response, error) in
guard let data = data else { return }
do
{
let result = try JSONDecoder().decode(Page.self, from: data)
for main in result.mainz {
print(main.humidity)
}
}catch
{print("Figure it out")
}
})
task.resume()

Answer 1

Create structures to capture whatever you want. For example, if you're interested in the temperatures and the coordinates, create structures for those:
struct WeatherTemperature: Codable {
let temp: Double
let pressure: Double
let humidity: Double
let tempMin: Double
let tempMax: Double
}
struct WeatherCoordinate: Codable {
let latitude: Double
let longitude: Double
enum CodingKeys: String, CodingKey {
case latitude = "lat"
case longitude = "lon"
}
}
Then create a structure for the whole response:
struct ResponseObject: Codable {
let coord: WeatherCoordinate
let main: WeatherTemperature
}
Note, I only create properties for those keys I care about.
And then decode it:
let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
do {
let responseObject = try decoder.decode(ResponseObject.self, from: data)
print(responseObject.coord)
print(responseObject.main)
} catch {
print(error)
}
That resulted in:
WeatherCoordinate #1(latitude: 27.760000000000002, longitude: -82.260000000000005)
WeatherTemperature #1(temp: 66.239999999999995, pressure: 1021.0, humidity: 63.0, tempMin: 62.600000000000001, tempMax: 69.799999999999997)
Clearly, add whatever other structures/properties you care about, but hopefully this illustrates the idea.
Note, I'd rather not let the JSON dictate my property names, so, for example, I specified a key decoding strategy for my decoder to convert from JSON snake_case to Swift camelCase.
I also like longer property names, so where I wanted more expressive names (latitude and longitude rather than lat and lon), I defined CodingKeys for those. But do whatever you want on this score.