How To Handle json null values in Swift - json

Question

I am playing With JSON for last two days and facing alot of curious problems and thanks to stack overflow it helps me. This is JSON featured key has two types of String values.
"featured":"1"
or
"featured": null,
I tried a lot to handle this but failed
Step 1:
if dict.objectForKey("featured") as? String != nil {
featured = dict.objectForKey("featured") as? String
}
Step 2:
let null = NSNull()
if dict.objectForKey("featured") as? String != null {
featured = dict.objectForKey("featured") as? String
}
Step 3:
if dict.objectForKey("featured") as? String != "" {
featured = dict.objectForKey("featured") as? String
}
but unfortunately can't found solution, you answer will be appreciated.

Answer 1

Try This
func nullToNil(value : AnyObject?) -> AnyObject? {
if value is NSNull {
return nil
} else {
return value
}
}
object.feature = nullToNil(dict["feature"])
Here, you can use this method, which will convert null value to nil and wont' cause crash in your app.
You can also use as?
object.feature = dict["feature"] as? NSNumber
Thanks.

Answer 2

Here is a working code, type cast operator(as?) will do the trick here. Null will not be typecasted into String, so the execution will go to failure block.
if let featured = dict["featured"] as? String {
print("Success")
}
else {
print("Failure")
}

Answer 3

Try this!
if let demoQuestion = dict.objectForKey("featured"){
let getValue: String = demoQuestion as! String
}
else {
print("JSON is returning nil")
}

Answer 4

Optional chaining with if let or its counterpart guard let is the way to go. All three steps combined (missing, wrong type - NSNull too, empty string):
guard let featured = dict.objectForKey("featured") as? String where !value.isEmpty else {
print("featured has wrong value")
}
// do what you need to do with featured
If you want to know more about optional chaining check out documentation

Answer 5

Hi you can use below function to remove null to empty string and prevent crashes
func removeNullFromDict (dict : NSMutableDictionary) -> NSMutableDictionary
{
let dic = dict;
for (key, value) in dict {
let val : NSObject = value as! NSObject;
if(val.isEqual(NSNull()))
{
dic.setValue("", forKey: (key as? String)!)
}
else
{
dic.setValue(value, forKey: key as! String)
}
}
return dic;
}
and before giving dict to any method call function in below way
let newdict = self.removeNullFromDict(dict: dict);

Answer 6

i did a static func to convert value from json to optional String.
class Tools{
static func setOptionalStr(value : Any?) -> String?{
guard let string = value as! String?, !string.isEmpty else {
return nil
}
return value as? String
}
}
In my controller
let urlStats: String? = Tools.setOptionalStr(value: json["UrlStats"])
i'm open to your feedback