How to handle JSON response with nil using guard in Swift - ios

Question

I just want to ask how to handle JSON return with null values in Swift.
I used guard for unwrapping the values, but if the JSON has a null value like in the example below, guard will not be executed
I also want to know proper way of using a guard. Is it okay to use multiple conditions in one guard? Like in my sample code below?
{
"error_code": "0",
"error_description": [],
"status": true,
"results": {
"id": 25,
"email": "jaundelacruz#yahoo.com",
"created_at": "2016-12-10T15:54:03.779Z",
"updated_at": "2016-12-15T06:41:49.432Z",
"first_name": "Juan",
"last_name": "Cruz",
"middle_name": "Dela",
"nickname": "joe",
"option_nickname": null,
"age": 24,
"gender": "Male",
"mobile_number": "639959283721",
"photo_url": {
"url": null
},
"school": "University of the Philippines",
"user_address": null,
"city": "Quezon City",
"country": null,
"longtitude": 121.0621301,
"latitude": 14.5832954,
"facebook_user_id": null,
"device_token": null,
"token": "YrxVEWUMYxieFy7PEsAn",
"is_sent": false,
"show_nickname": false
},
"error": []
}
Here's my code:
func UserLogin(facebookID: String) -> Void {
UIApplication.shared.isNetworkActivityIndicatorVisible = true
let urlString = Constants.baseURL + Constants.apiURL + Constants.loginUrl
let params:Dictionary<String, AnyObject> = [
"facebook_id": facebookID as AnyObject
]
Alamofire.request(urlString, method: .post, parameters: params, encoding: JSONEncoding.default)
.validate()
.responseJSON { response in
switch response.result {
case .success:
let userjson = JSON(data: response.data!)
let results = userjson["results"].dictionaryValue
guard let auth_token = results["token"]?.string,
let userid = results["id"]?.int,
let firstname = results["first_name"]?.string,
let lastname = results["last_name"]?.string,
let nickname = results["nickname"]?.string,
let city = results["city"]?.string,
let photo = results["photo_url"]?["url"]else{
//nil
return
}
//The Process will not continue from here if the JSON response has a null value)
self.userdefault.saveUserToken(authToken: auth_token)
self.userdefault.setUserID(userID: userid)
self.userdefault.setuserFirstName(userFName: firstname)
self.userdefault.setuserLastName(userLName: lastname)
self.userdefault.setuserNickName(userNName: nickname)
self.userdefault.setuserCity(userCity: city)
self.GotoMainNavigation()
case .failure(let error):
print("susb \(error)")
self.getFacebookInfo()
}
UIApplication.shared.isNetworkActivityIndicatorVisible = false
}
}
Thank you

Answer 1

Your guard expression is perfectly fine and filters all null values except in the last line. Assuming the url is also a string you have to check
let photo = results["photo_url"]?["url"]?.string ...
but consider that the guard expression will only be evaluated to true if all optional bindings succeed.
For example if the photo value is supposed to be optional put it after the guard expression and use the nil coalescing operator:
let photo = results["photo_url"]?["url"]?.string ?? ""

Answer 2

data = {
results = {
resultsData = (
{
a = "A";
b = "B";
c = "C":
}
);
};
};
guard is a new conditional statement that requires execution to exit the current block if the condition isn’t met. Any new optional bindings created in a guard statement’s condition are available for the rest of the function or block, and the mandatory else must exit the current scope, by using return to leave a function, continue or break within a loop, or a #noreturn function
guard let data = response["data"] as? [String:AnyObject],let resultsObj = response["results"] as? [String:AnyObject],let resultsData = results["resultsData"] as? [String:AnyObject] else{
return
}