In iOS8 and prior I can use:
NSString *str = ...; // some URL NSString *result = [str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
Objective-C
this code work for me :
urlString = [urlString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLFragmentAllowedCharacterSet]];