Question

How to know whether NSUserDefaults contains any value?How to check whether its empty?

Answer 1

There isn’t a way to check whether an object within NSUserDefaults is empty or not.
However, you can check whether a value for particular key is nil or not.

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];

NSObject * object = [prefs objectForKey:@"your_particular_key"];
if(object != nil){
   //object is there
}