Hasan Nizamani Hasan Nizamani - 5 months ago 36
Swift Question

Simple and clean way to convert JSON string to Object in Swift

I have been searching for days to convert a fairly simple JSON string to an object type in Swift but with no avail.

Here is the code for web service call:

func GetAllBusiness() {

Alamofire.request(.GET, "http://MyWebService/").responseString { (request, response, string, error) in

println(string)

}
}


I have a swift struct Business.swift:

struct Business {
var Id : Int = 0
var Name = ""
var Latitude = ""
var Longitude = ""
var Address = ""
}


Here is my test service deployed:

[
{
"Id": 1,
"Name": "A",
"Latitude": "-35.243256",
"Longitude": "149.110701",
"Address": null
},
{
"Id": 2,
"Name": "B",
"Latitude": "-35.240592",
"Longitude": "149.104843",
"Address": null
}
...
]


It would be a delight if someone guide me through this.

Thanks.

Answer

Here are some tips how to begin with simple example.

Consider you have following JSON Array String (similar to yours) like:

 var list:Array<Business> = []

  // left only 2 fields for demo
  struct Business {
    var id : Int = 0
    var name = ""               
 }

 var jsonStringAsArray = "[\n" +
        "{\n" +
        "\"id\":72,\n" +
        "\"name\":\"Batata Cremosa\",\n" +            
        "},\n" +
        "{\n" +
        "\"id\":183,\n" +
        "\"name\":\"Caldeirada de Peixes\",\n" +            
        "},\n" +
        "{\n" +
        "\"id\":76,\n" +
        "\"name\":\"Batata com Cebola e Ervas\",\n" +            
        "},\n" +
        "{\n" +
        "\"id\":56,\n" +
        "\"name\":\"Arroz de forma\",\n" +            
    "}]"


        // convert String to NSData
        var data: NSData = jsonStringAsArray.dataUsingEncoding(NSUTF8StringEncoding)!
        var error: NSError?

        // convert NSData to 'AnyObject'
        let anyObj: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions(0),
            error: &error)
        println("Error: \(error)")

     // convert 'AnyObject' to Array<Business>
     list = self.parseJson(anyObj!)

     //===============

    func parseJson(anyObj:AnyObject) -> Array<Business>{

        var list:Array<Business> = []

         if  anyObj is Array<AnyObject> {

            var b:Business = Business()

            for json in anyObj as Array<AnyObject>{
             b.name = (json["name"] as AnyObject? as? String) ?? "" // to get rid of null
             b.id  =  (json["id"]  as AnyObject? as? Int) ?? 0                 

               list.append(b)
            }// for

        } // if

      return list

    }//func    

[EDIT]

To get rid of null changed to:

b.name = (json["name"] as AnyObject? as? String) ?? ""
b.id  =  (json["id"]  as AnyObject? as? Int) ?? 0 

See also Reference of Coalescing Operator (aka ??)

Hope it will help you to sort things out,