unable to download json data too large in swift - ios

Question

I tried downloading data to JSON from a webserver that accepts username and password input in a json format. Once I have authenticated, I have to download json data. So I used this method
let postString = ["user":"user1", "pwd": "pass1"]
var request = URLRequest(url:URL(string:"http://vdctest.agrishare.com/list_up")!)
request.httpMethod = "POST"
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")
request.addValue("application-idValue", forHTTPHeaderField: "secret-key")
request.httpBody = try! JSONSerialization.data(withJSONObject: postString, options:.prettyPrinted)
let session = URLSession.shared
//Post
session.dataTask(with: request){data, response, err in
//Guard: ws there error ?
guard(err == nil) else {
print("err")
return
}
//Guard: check was any data returned?
guard let data = data else{
print("no data return")
return
}
//Convert Json to Object
let parseResult: [String:AnyObject]!
do{
parseResult = try JSONSerialization.jsonObject(with: data, options:.allowFragments) as! [String:AnyObject]
print("\(parseResult)")
} catch {
print("Could not parse data as Json \(data)")
return
}
//Check jsonDictionary
guard let jsonArray = parseResult["success"] as? [String:AnyObject] else{
print("jsonDictionary error")
return
}
//check jsonArray and switch to LoginViewController
if(jsonArray.count == 0 ){
print("jsonArray not found")
return
} else{
DispatchQueue.main.async{
let loginvc = LoginViewController()
self.present(loginvc, animated: true, completion: nil)
print(jsonArray)
}
}
}.resume()
}
When I run the app, the terminal says:
Could not parse data as Json 1520 bytes
Why?
Output:
Could not parse data as Json: Error Domain=NSCocoaErrorDomain
Code=3840 "Invalid value around character 0."
UserInfo={NSDebugDescription=Invalid value around character 0.}

Answer 1

You likely do not have valid JSON -- as the error states, right around the very first character. Valid JSON is going to either be a single Object that opens and closes with a { and } or an Array of Objects, opening and closing with a [ and ].
Please post a bit of the returned JSON to confirm.
EDIT: Also -- if you are requesting an http resource, and not https, you need to add the server to the allowed unsecure servers list.