Can't set NSUserDefaults value through variable in IOS - ios

Question

In my iOS app when I'm logging in I used set UserID and loginstatus into NSUserDefaults like this.
#implementation Login{
NSInteger UserId;
NSUserDefaults *preferences;
}
- (IBAction)LogInClick:(UIButton *)sender {
[preferences setInteger:UserId forKey:#"UserId"]; //UserId=40;
[preferences setBool:YES forKey:#"loginstatus"];
[preferences synchronize];
NSLog(#"All NSUserDefaults: %#", [[NSUserDefaults standardUserDefaults] dictionaryRepresentation]);
NSString *uID = [preferences stringForKey:#"UserId"];
NSLog(#"UserID: %#",uID);
}
But the values are not setting in the NSUserDefaults. I tried to log all NSUserDefaults value and also the single UserID value but all fields are coming null.
Later I use this code to logout
- (IBAction)LogOutClick:(UIButton *)sender {
[[NSUserDefaults standardUserDefaults] setObject:0 forKey:#"UserId"];
[[NSUserDefaults standardUserDefaults] setObject:NO forKey:#"loginstatus"];
/* [preferences setInteger:0 forKey:#"UserId"];
[preferences setBool:NO forKey:#"loginstatus"];
[preferences synchronize];*/
NSLog(#"All NSUserDefaults: %#", [[NSUserDefaults standardUserDefaults] dictionaryRepresentation]);
}
First when i logged out it all sets to zero and now the values are not setting. Can anybody tell me what the problem is?

Answer 1

That's because NSUserDefaults *preferences; is just a pointer. And it's value is nil, I presume. You should initialize it. For instance:
- (IBAction)LogInClick:(UIButton *)sender {
preferences = [NSUserDefaults standardUserDefaults];
[preferences setInteger:UserId forKey:#"UserId"]; //UserId=40;
[preferences setBool:YES forKey:#"loginstatus"];
[preferences synchronize];
...
May be a more logical place to initialize preferences would be an init method, or something else that you would consider appropriate for this purpose.

Answer 2

You haven't get the standard userdefaults reference. Change this method
- (IBAction)LogInClick:(UIButton *)sender {
preferences = [NSUserDefaults standardUserDefaults];
[preferences setInteger:UserId forKey:#"UserId"]; //UserId=40;
[preferences setBool:YES forKey:#"loginstatus"];
[preferences synchronize];
NSLog(#"All NSUserDefaults: %#", [[NSUserDefaults standardUserDefaults] dictionaryRepresentation]);
NSString *uID = [preferences stringForKey:#"UserId"];
NSLog(#"UserID: %#",uID);
}