Graphics Programs Reference
In-Depth Information
custom classes, which typically have names that sound like data-bearing objects, such as
InsurancePolicy
or
PlayerHistory
.
View and model objects are the factory workers of an application - they focus tightly on
specific tasks. For example, an instance of
UILabel
(a view object) knows how to dis-
play text in a given font within a given rectangle. An
NSString
instance (a model ob-
ject) knows how to store a character string. But the label doesn't know
what
text it should
display, and the string doesn't know
what
characters it should store.
This is where
controller objects
come in. Controllers are the managers in an application.
They keep the view and model objects in sync, control the “flow” of the application, and
save the model objects out to the filesystem (
Figure 1.11
). Controllers are the least reus-
able classes that you will write, and they tend to have names like
ScheduleControl-
ler
and
ScoreViewController
.
Figure 1.11 MVC pattern
When you create a new iOS project from a template, the template automatically makes a
controller object for you. For
Quiz
, this controller is the
QuizViewController
. Most
applications have more than one controller object, but a simple application like
Quiz
only
needs one. (Actually, the template creates another controller for
Quiz
- the
QuizAp-
pDelegate
. Every iOS application has an “app delegate” object, and it is the primary
controller of the application. However, to keep things simple, we won't use the app deleg-
