Alamofire parse response incorrectly - json

Question

Trying out the request on Postman, the "data" of the response is an empty dictionary.
However, when I try that in swift using Alamofire, "data" gets misinterpreted as an empty array. What could I be doing wrong?
Raw response using debugPrint(response) prints the following:
[Response]:
[Status Code]: 200
[Headers]:
Access-Control-Allow-Origin: *
Alt-Svc: h3=":443"; ma=2592000, h3-29=":443"; ma=2592000, h3-Q050=":443"; ma=2592000, h3-Q046=":443"; ma=2592000, h3-Q043=":443"; ma=2592000, quic=":443"; ma=2592000; v="43,46"
Cache-Control: no-cache, private
Content-Encoding: br
Content-Length: 71
Content-Type: application/json
Date: Tue, 31 Jan 2023 16:32:18 GMT
Vary: Accept-Encoding
x-powered-by: PHP/8.0.24
x-ratelimit-limit: 60
x-ratelimit-remaining: 59
[Body]:
{"status":false,"message":"Kullan\u0131c\u0131 bilgileri hatal\u0131.","data":[]}
Tried changing the encoding and headers of the request, none was helpful.

Answer 1

I've come across this odd way of representing null from a server (openweathermap), where instead of null, it uses {}.
To work with this, I used a custom decoder, something like:
// for the case where we have: "data": { } instead of, "data": null
public init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
if let theData = try? values.decode([String].self, forKey: .data) {
self.data = theData
} else {
self.data = nil
}
// ....other keys
}
with declaration, let data: [String]? or whatever the array holds.
Note this is a JSONDecoder behaviour, not Alamofire, I was using URLSession.shared... with this. When the JSONDecoder tries to decode this {}, it crashes, because it is not an a null and it not an array either. Postman is probably more forgiving than Swift JSONDecoder. Alamofire tries to decode data as an array, because you probably declared it as an array in your struct/class to decode.
EDIT-1:
here is the SwiftUI code I used to test my answer (same approach for UIKit and Alamofire):
struct RequestResponse: Decodable {
var status: Bool
var message: String?
var data: [String]?
enum CodingKeys: String, CodingKey {
case status, message, data
}
// for the case where we have: "data": { } instead of, "data": null
public init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
self.status = try values.decode(Bool.self, forKey: .status)
self.message = try values.decode(String?.self, forKey: .message)
if let theData = try? values.decode([String].self, forKey: .data) {
self.data = theData
} else {
self.data = nil
}
}
}
struct ContentView: View {
#State var response: RequestResponse?
var body: some View {
VStack {
if let results = response {
Text(results.status ? "true" : "false")
Text(results.message ?? "no message")
ForEach(results.data ?? [], id: \.self) { item in
Text("\(item)")
}
}
}
.onAppear {
let json = """
{
"status": false,
"message": "some message here",
"data": {}
}
"""
// simulated API data from the server
let data = json.data(using: .utf8)!
do {
let decoded = try JSONDecoder().decode(RequestResponse.self, from: data)
print("\n---> decoded: \(decoded) \n")
response = decoded
} catch {
print("\n---> error: \n \(error)\n")
}
}
}
}

Answer 2

This isn't an Alamofire issue, it's an error from JSONDecoder. You can check your actual response by printing the raw response in Alamofire (which you don't post any code for).
.response<...> { response in
debugPrint(response)
}
That will print a String version of the response body (unless it's very large) which you can use to see what you're actually receiving.
You can also check your actual response using a proxy like Proxyman or a traffic inspector like Wireshark and see what you're actually getting. It seems likely you're actually receiving an array.