Alamofire Failure - responseSerializationFailed

Question

func postAd(cryptoo: String, fiatt: String,locationn: String,countryy: String,marginn: String,
            pricee: String,minlimitt: String,maxlimitt: String,paymrntwindoww: String,paymrntmethodd: String,
            accountdetailss: String,infoo: String,termss: String
){
                    
    let endpoint = "https://new.demozab.com/armup/api/public/api/post-trade"
    
   // let params = ["email":"smith@mailinator.com","password":"Test@123"]
    
    let params = [
        
        "crypto_currency_id":"1",
        "trade_type": "buy",
        "location": "",
        "country": "1",
        "market":"15",
        "margin":"1",
        "trade_price":"1",
        "min_transaction_limit":"1",
        "max_transaction_limit":"1",
        "payment_method":"1",
        "payment_window":"1",
        "account_details": "1",
        "additional_information":"1",
        "sunday_start":"",
        "sunday_end":"",
        "monday_start":"",
        "monday_end":"",
        "tuesday_start":"",
        "tuesday_end":"",
        "wednesday_start":"",
        "wednesday_end":"",
        "thursday_start":"",
        "thursday_end":"",
        "friday_start":"",
        "friday_end": "",
        "saturday_start": "",
        "saturday_end": "",
        "terms":"i",
        
    ]
     guard let url = URL(string: endpoint)
    else {

        print("Invalid URL")
        return
    }
    let headers: HTTPHeaders = [
        "Authorization": "Bearer TVfXc1gPZbLfruJ53Q7PkkSDjSXi6gXGWXkCXg6j",
        "Content-Type": "application/json"
    ]



    AF.request( url, method: .post, parameters: params,  headers: headers ).responseDecodable(of: CommonData.self) {
        (response) in
       
      print(response.result)
        /////////            
        
        }   
    
}

API Response:

{
    "success": true,
    "message": "Advertisement Posted Successfully!"
}

Model Class:

import Foundation

// MARK: - CommonData
struct CommonData: Codable {
    let success: Bool
    let message: String
}

ERROR:

failure(Alamofire.AFError.responseSerializationFailed(reason: Alamofire.AFError.ResponseSerializationFailureReason.decodingFailed(error: Swift.DecodingError.typeMismatch(Swift.String, Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "message", intValue: nil)], debugDescription: "Expected to decode String but found a dictionary instead.", underlyingError: nil)))))

Try to post API call.

Answer 1

When you have a successfull POST, the response is CommonData as you have it.

However, when there is some error, then you get CommonData2 (see below).

For example in your params, a "location": "" is required. Similarly with "max_transaction_limit": "2", note it is > 1. In those cases you have to decode CommonData2.

Same when you use let params = ["email":"smith@mailinator.com","password":"Test@123"], you get CommonData2 response.

 struct CommonData2: Codable {
     let success: Bool
     let result: String?
     let message: Message
 }

 struct Message: Codable {
     let errors: [String: [String]]
 }

To decode both types of responses, you could try this approach, using init(from decoder: Decoder), works for me:

 struct CommonData2: Codable {
     let success: Bool
     let result: String?
     let message: Message?
     var msg: String?
     
     enum CodingKeys: String, CodingKey {
         case success, message, result
     }
     
     init(from decoder: Decoder) throws {
         let container = try decoder.container(keyedBy: CodingKeys.self)
         self.result = try? container.decode(String.self, forKey: .result)
         self.success = try container.decode(Bool.self, forKey: .success)
         if let theMessage = try? container.decode(Message.self, forKey: .message) {
             self.message = theMessage
         } else {
             self.message = nil
         }
         if let theString = try? container.decode(String.self, forKey: .message) {
             self.msg = theString
         } else {
             self.msg = nil
         }
     }

 }