JSON encoding with backslashes

Question

I m using Alamofire and SwiftyJSOn to parse JSON output. It works very well however some sites give json with escaped output. I use Alamofire like below

    Alamofire.request(.POST, url, parameters: param, encoding: .JSON)
        .responseJSON { (req, res, json, error) in
         var json = JSON(json!)

Site gives me JSON result with escaped string so SwiftyJSON can't decode it. How can I convert below

{
    "d": "{\"UniqeView\":{\"ArrivalDate\":null,\"ArrivalUnitId\":null,\"DeliveryCityName\":null,\"DeliveryTownName\":null},\"ErrorMessage\":null,\"Message\":null,\"IsFound\":false,\"IsSuccess\":true}"
}

to something like

{
       "d": {
          "UniqeView": {
             "ArrivalDate": null,
             "ArrivalUnitId": null,
             "DeliveryCityName": null,
             "DeliveryTownName": null
          },
          "ErrorMessage": null,
          "Message": null,
          "IsFound": false,
          "IsSuccess": true
       }
    }

Answer 1

Here is another approach for Swift 4 - Using Codable

This was the json that I received:

{
    "error_code": 0,
    "result": {
        "responseData": "{\"emeter\":{\"get_realtime\":{\"voltage_mv\":237846,\"current_ma\":81,\"power_mw\":7428,\"total_wh\":1920,\"err_code\":0}}}"
    }
} 

The JSON part with backslashes is equal to this:

{
    "emeter": {
        "get_realtime": {
            "voltage_mv": 237846,
            "current_ma": 81,
            "power_mw": 7428,
            "total_wh":19201,
            "err_code":0
        }
    }
}

And this was the code that I used:

import Foundation

class RealtimeEnergy: Codable {
    let errorCode: Int
    let result: ResultRealtimeEnergy?
    let msg: String?

    enum CodingKeys: String, CodingKey {
        case errorCode = "error_code"
        case result, msg
    }

    init(errorCode: Int, result: ResultRealtimeEnergy?, msg: String?) {
        self.errorCode = errorCode
        self.result = result
        self.msg = msg
    }
}

class ResultRealtimeEnergy: Codable {

    let responseData: String
    var emeter: Emeter

    enum CodingKeys: String, CodingKey {
        case responseData
    }

    required init(from decoder: Decoder) throws {

        let container = try decoder.container(keyedBy: CodingKeys.self)
        responseData = try container.decode(String.self, forKey: .responseData)
        let dataString = try container.decode(String.self, forKey: .responseData)
        emeter = try JSONDecoder().decode(Emeter.self, from: Data(dataString.utf8))
    }
}



class Emeter: Codable {
    let emeter: EmeterClass

    init(emeter: EmeterClass) {
        self.emeter = emeter
    }
}

class EmeterClass: Codable {
    let getRealtime: GetRealtime

    enum CodingKeys: String, CodingKey {
        case getRealtime = "get_realtime"
    }

    init(getRealtime: GetRealtime) {
        self.getRealtime = getRealtime
    }
}

class GetRealtime: Codable {
    let voltageMv, currentMa, powerMw, totalWh: Int
    let errCode: Int

    enum CodingKeys: String, CodingKey {
        case voltageMv = "voltage_mv"
        case currentMa = "current_ma"
        case powerMw = "power_mw"
        case totalWh = "total_wh"
        case errCode = "err_code"
    }

    init(voltageMv: Int, currentMa: Int, powerMw: Int, totalWh: Int, errCode: Int) {
        self.voltageMv = voltageMv
        self.currentMa = currentMa
        self.powerMw = powerMw
        self.totalWh = totalWh
        self.errCode = errCode
    }
}

And this is the trick:

emeter = try JSONDecoder().decode(Emeter.self, from: Data(dataString.utf8))

Answer 2

// This Dropbox url is a link to your JSON
// I'm using NSData because testing in Playground
if let data = NSData(contentsOfURL: NSURL(string: "https://www.dropbox.com/s/9ycsy0pq2iwgy0e/test.json?dl=1")!) {

    var error: NSError?
    var response: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.allZeros, error: &error)
    if let dict = response as? NSDictionary {
        if let key = dict["d"] as? String {

            let strData = key.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)
            var error: NSError?
            var response: AnyObject? = NSJSONSerialization.JSONObjectWithData(strData!, options: NSJSONReadingOptions.allZeros, error: &error)

            if let decoded = response as? NSDictionary {
                println(decoded["IsSuccess"]!)   // => 1
            }

        }
    }
}

I guess you have to decode twice: the wrapping object, and its content.

Answer 3

@ericd comments helped me to solve the issue. I accepted his answer for this question. Since I am using Alamofire for asynchronous operation, and SwiftyJSON, I couldn't use his code. Here is the code with Alamofire and SwiftyJSON.

Alamofire.request(.POST, url, parameters: param, encoding: .JSON)
   .responseJSON { (req, res, json, error) in
    if(error != nil) {
        NSLog("Error: \(error)")
        failure(res, json, error)
    }
    else {

        var jsond = JSON(json!)
        var data = jsond["d"].stringValue.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)
        jsond = JSON(data: data!)