Week 2, Thursday

gistfile1.txt

Question 1:
A) Programmer needs to set up the Observee (Subject) object adding a new notification to NSNotificationCenter defaultCenter. 
After doing this, each Observer who needs to be notified needs to subscribe to that notification. To do that, each Observer
object needs to be added as a Observer in NotificationCenter and define a method that will be called each time that it receives
a new notification.
B) Notification Center uses two different design patterns: the Observer and the Singleton pattern. The observer defines that 
any object that wants to subscribe to receive notifications (that could be also considered delegates for that observer, because
they can execute a specific task when receive a notification) can do that. In the delegation pattern, only one object can 
receive a "notification" by the delegator. Notification Center uses a Singleton Pattern to define that only one instance 
of this class will be created during the execution of the application.
C) Asynchronouly. All subscribers of the notification receives the message in the same time, and can execute their specific 
tasks by their own.

Question 2: 
Self should avoid reference itself, because this may cause a retain cycle.

Question 3:
A) Based on the code provided, it looks like both classes are View Controllers (the first is a subclass of UIViewController and the second directly access a input view - so it is not a model - and also wants to receive a notification when a person class is saved - so it is not a view, according to MVC patterns). In this case, the best option would be use the delegation pattern. Simplified code below:
@protocol ZZPersonViewControllerDelegate
- (void) personWasSaved:(Person*)p;
- (void) personWasDiscarded:(Person*)p;
@end

@interface ZZPersonViewController
  @property id<ZZPersonViewControllerDelegate> delegate;
@end

@implementation ZZPersonViewController
- (void) savePerson
{
  if(ok)
    [self.delegate personWasSaved:p];
  else
    [self.delegate personWasDiscarded:p];
}
@end

// in the other class...
// first, remove line codes where notification center is being referred
@interface .... <ZZPersonViewControllerDelegate>
@end

@implementation
- (void) personWasSaved:(Person*)p
{
}
- (void) personWasDiscarded:(Person*)p
{
}
@end

B) Considering that in a MVC pattern the responsible to maintain all object data is the Model, all code that is referencing the cloud manager should be transferred to the ZZPerson class.

Question 4: Properties encapsulates the object information from external user (more safety). Also, through the getter and
setter methods, you could do execute specific tasks before returning the value (integrity). For example, you could create
a "Chance of Rain %" and does not allow values outside 0 and 100 in the setter. Or before returning a name, you could
return in Uppercase in the getter, without having to change the instance variable real value.