iOS Coding Best Practices

2. Agenda
• Project Structure
• Design Patterns & Architecture
• Storing Data
• Coding Conventions

3. What main design pattern does
Apple recommend for
structuring
your iOS projects?

4. Model-View-Controller
Controller
Update
Coordination Changes
Changes Update
Model Data View
Display

5. Default Project
• Notice Classes is a
catch-all default
‘’bucket’’ for code

6. MVC Formatted Project
• Remove references
• Create class folders
in Finder
• AppDelegate
• Controllers
• Helpers
• Models
• Drag into Xcode

7. According to Apple, should the
model, view or controller be used
to capture events?

8. Roles & Responsibilities
• Model
• Data/Algorithms/Networking
• Most of your custom code lives here
• View
• Display/Event Capture/Visual Appeal
• Don’t try to reinvent UIKit, use it
• Controller
• Coordination/Delegation/Odd Jobs
• Transitions, Startup/Shutdown

9. Is this a good pattern & why?
Update

10. Don’t cut out the controller!
Avoid bi-directional messaging
Reject
Delay
Validate
Update
• Network Access
• Multiple
Choices
• Commit

11. Is this a good pattern & why?

12. Loose Coupling
• Don’t skip MVC layers when messaging
• Use controllers to coordinate messages
• Don’t mix MVC roles in one object
• Don’t gather too much work in one place
• Don’t declare data in your view classes
• Maintenance nightmare
• You can display data in a view, just don’t store it

13. What are three of the design
patterns used to communicate
between the model, view &
controller?

14. Communication Between Objects
Target-Action Notification Delegation
Reuse controls without Broadcast changes Control reuse
subclassing “Yes”
« When tapped, call this
method » « Software keyboard “End Editing?”
-setTarget:(id)target action:(SEL)action…about to appear! » UIKit (UIScrollView, ect)
NSNotificationCenter Will/Did/Should
-(void)scrollViewDidZoom:

15. How do you create a custom
controller to split the screen in two
parts?

16. You Don’t!
Use the UISplitViewController
• Don’t try to reinvent the wheel
• UIKit has a lot of the base controls you need
• Really question whether you need a custom
control (and if it exists already)
• Don’t misuse framework classes
• ie Removing views from UIViewControllers
• Don’t try to reinvent the way models, views &
controllers talk to each other
• Use delegates & notifications

17. Is this a good pattern & why?
-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
if ([scrollView isKindOfClass:[UITableView class]}){
// do something
} else {
// use UIScrollView logic
}

18. Class checks in delegate methods
Code unmanagable over time - EverythingControllers
Coding horror - iOS version of a GOTO
Correct Approach on
iPad
Parcel out your
controllers

19. MANDATORY: ALWAYS write/model out your
iOS app design before coding!
At first, I was like… But then, it was like…
(in your brain) (in the repo)

20. Creating an MVC diagram of your project
• Means you thought through the architecture
• Means you know how the code will be organized
physically & logically
• Means you potentially avoided structural bugs
• Easier to validate with the team
• High quality projects & happy clients

22. What’s the optimal architecture for
a Universal Application?

23. Optimal Universal App Architecture
iPhone App iPad App
UI Framework (Views & Controllers)
Non-UI Framework (Networking & Models)

24. Photo Sharing Application
Data from the model
is in both the inspector
and in the toolbar

25. MVC Structure
Update Change
Change
Update

26. What are the six primary ways of
storing data on iOS?

27. Six Model Options
• Property Lists
• Archives
• Custom Files
• Server/iCloud/APIs
• SQLite
• CoreData

28. According to Apple, what data should
you store in your App
Defaults/Preferences?

29. Don’t store data in settings!
• Wrong tool for the job
• App may get rejected
• Settings Panel test
• On/Off Advanced Features

30. What should you use for quick storage
of
strings, numbers, arrays, dictionaries, e
ct?

31. Property Lists.

32. What should you use to store partial
graphs?

33. CoreData
• Modeling Tools
• Simple save/restore
• Queries
• Data Protection
• Ordered Relationships
• UIManagedDocument
• Partial Graphs
• Undo
• Incremental Stores
• ect…

34. What should you use to include data
with queue-based concurrency in your
app?

35. CoreData again.

36. What should you use if you are dealing
with a lot of legacy code or data, or you
need to create an NSObject-based
graph?

37. Custom Files.

38. When would you want to use a data
archive?

39. For easily « serializing »
and « deserializing »
objects in a data file.

40. What are the two primary features of
SQLite?

41. Provides Database functionality for iOS apps
Supports Object Relational Mapping

42. Know Your Data Model Options
• Property Lists
• Archives
• Custom Files
• Server/iCloud/APIs
• SQLite
• CoreData

43. Coding Conventions
• Brace style for if-else
• Parenthesis style
• Leading underscores
• Code indenting
• CapitalizationStyle (ie capitalization_style)
Check out the Google iOS Style guide &
Apple docs: http://google-
styleguide.googlecode.com/svn/trunk/objcguide
.xml

44. What is KVO?

45. Key-Value Observing (KVO)
• Requires your code to be compliant
• Follow style guide
• Instrument your own notifications
• Automatic Change Notifications for your objects