Mapping Generic API Response Using Codable or ObjectMapper

Question

I am facing a challenge regarding mapping a generic api responses against a model class using codable or object mapper. Suppose I have these api responses against different apis.

{
  "code" : 0, 
  "http_response" : 200,
  "success" : true, 
  "data" : user
}

{
  "code" : 0, 
  "http_response" : 200,
  "success" : true, 
  "data" : locations
}

{
  "code" : 0, 
  "http_response" : 200,
  "success" : true, 
  "data" : countries
}

here user, locations and countries are separate codable/mapper classes.

I will have to construct a class like this

struct APIResponse : Codable {
    let success : Bool?
    let http_response : Int?
    let code : Int?
    let data : ??
}

How I will construct my base class to handle these responses using one class or I will have construct different classes just to change "data" type according to value?

Any kind of help or suggestion will be highly appreciated.

Thanks

Answer 1

Make generic constraint for you struct which says that T has to conform to Decodable and then use this type for specifing type of data

struct APIResponse<T: Decodable>: Decodable {
    var code, httpResponse: Int
    var success: Bool
    var data: T
}

struct User: Decodable {
    var name: String
}

---

note that I changed name of httpResponse parameter since I'm using keyDecodingStrategy which converts http_response to httpResponse

---

Then while decoding specify type of T

Single object

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase

do {
    let responses = try decoder.decode([APIResponse<User>].self, from: data)
    let user = responses[0].data /* data of type `User` of specific response */
} catch { print(error) }

Array of objects

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase

do {
    let responses = try decoder.decode([APIResponse<[User]>].self, from: data)
    let users = responses[0].data /* data of type `[User]` of specific response */
} catch { print(error) }