#define USERNAME_KEY @"username"
#define PASSWORD_KEY @"password"

-(void) saveUser:(NSString *) username andPassword:(NSString *) password {
	NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
	// Save the username.
	[userDefaults setObject:username forKey:USERNAME_KEY];
	[userDefaults synchronize];

	// Save the password.
	[userDefaults setObject:password forKey:PASSWORD_KEY];
	[userDefaults synchronize];
}

-(void) someFunction {
	NSString *username = [[NSUserDefaults standardUserDefaults] objectForKey:USERNAME_KEY];
}