Accessing Object Attributes from JSON, Swift3 - json

Question

let url = URL(string: "http://192.168.30.243:5000/trippy/destination/info?id=4864cc0a-8")
let task = URLSession.shared.dataTask(with: url!) { (data, response, error) in
if error != nil {
print ("ERROR")
}
else {
if let content = data {
do {
//Array
let myJson = try JSONSerialization.jsonObject(with: content, options: JSONSerialization.ReadingOptions.mutableContainers) as AnyObject
print(myJson)
if let information = myJson as? NSDictionary {
print (information.value(forKey: "EmergencyNumbers")!)
if let number = information.value(forKey: "EmergencyNumbers") as? NSArray {
//This is the part I am unsure about
if let description = number[0] as? AnyObject {
//I know do not know how to access the object's attribute values
}
}
}
}
catch {
}
}
}
}
task.resume()
}
I have used JSON to parse data from the web. I have utilized a dictionary to access the information and then an array to get the data from the certain key. Within this array are lie some objects. How do I access each of these objects' properties' values?
JSON Example:
{
Currency = testCurrency;
DestinationId = "4864cc0a-8";
DialCode = testDialCode;
DoesntUseMetricSystem = 0;
DrinkingAge = 16;
DriverLicense = 1;
EmergencyNumbers = (
{
Description = "Emergency Pizza Delivery";
Id = 1;
Number = 6969;
}
);
Id = 1;
IsNorthHemisphere = 1;
OfficialLanguage = {
Id = 1;
Name = testLanguage;
};
PowerGridVoltage = 226;
PowerSocket = dk;
Telecoms = nonern;
Tipping = 2;
WidelySpokenLanguages = (
{
Id = 2;
Name = testtLanguage;
}
);
WrongSideOfRoad = 0;
}

Answer 1

I see you are coming from Objective-C world, so first I'd recommend you give up using NSArray, NSDictionary etc. in favor of their Swift counterparts Array and Dictionary:
let task = URLSession.shared.dataTask(with: url!) { data, response, error in
...
let JSON = try? JSONSerialization.jsonObject(with: data!, options: [])
if let dictionary = JSON as? [String: Any],
let emergencyNumbers = dictionary["EmergencyNumbers"] as? [[String: Any]]
{
emergencyNumbers.forEach { numbers in
print(numbers["Description"] as? String)
print(numbers["Id"] as? Int)
print(numbers["Number"] as? Int)
}
}
}
By the way [String: Any] is just a syntactic sugar for Dictionary<String, Any>. Same applies to arrays as well: [[String: Any]] is for Array<Dictionary<String, Any>>.

Answer 2

As always, don't use NSArray / NSDictionary in Swift. You throw away the type information.
The root object is a dictionary ([String:Any]), the value for key EmergencyNumbers is an array ([[String:Any]]). Use a loop to iterate thru the array.
if let root = try JSONSerialization.jsonObject(with: content) as? [String:Any] {
print(myJson)
if let emergencyNumbers = root["EmergencyNumbers"] as? [[String:Any]] {
for emergencyNumber in emergencyNumbers {
let description = emergencyNumber["Description"] as? String
let id = emergencyNumber["Id"] as? Int
let number = emergencyNumber["Number"] as? Int
print("description", description ?? "n/a")
print("id", id ?? "n/a")
print("number", number ?? "n/a")
}
}
Some other bad habits:
.mutableContainers is completely meaningless in Swift. The hilarious thing is, everybody who passes the option .mutableContainers assigns the result to an immutable constant.
The unspecified JSON type in Swift 3+ is Any not AnyObject
valueForKey, a KVC method, is inappropriate for this purpose, use objectForKey or key subscription. With Swift native types don't use it at all.