ios coding best practices

iOS Coding Best PracticesJean-Luc David

CTO, Digiflare Inc

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

What main design pattern does Apple recommend for structuringyour iOS projects?

Model-View-Controller

Controller

Model View

Model Data

View Display

Controller Coordination Changes

Update

Update

Changes

Default Project

• Notice Classes is a catch-all default ‘’bucket’’ for code

MVC Formatted Project• Remove references• Create class folders

in Finder• AppDelegate• Controllers• Helpers• Models

• Drag into Xcode

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

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

Is this a good pattern & why?

Controller

ViewModel

Update

Don’t cut out the controller!Avoid bi-directional messaging

Controller

ViewModel

Update

RejectDelay

Validate

• Network Access

• Multiple Choices

• Commit

“Home” Controller

“Social” Controller

“Settings” Controller

“Home” View “Social” View “Settings” View

“Home” Model “Social” Model“Settings”

Model

Is this a good pattern & why?

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

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

Communication Between Objects

Target-Action Notification Delegation

UIButton UIKeyboard

Target

Reuse controls without subclassing

« When tapped, call this method »

-setTarget:(id)target action:(SEL)action…

Observer

Observer« Software keyboard

about to appear! »NSNotificationCenter

Broadcast changes

UITextField

Delegate

“Yes”

“End Editing?”

Control reuse

UIKit (UIScrollView, ect)Will/Did/Should

-(void)scrollViewDidZoom:

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

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

UIViewController

UIScrollView

Is this a good pattern & why?

UITableView

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{ if ([scrollView isKindOfClass:[UITableView class]}){ // do something } else { // use UIScrollView logic}

Class checks in delegate methodsCode unmanagable over time - EverythingControllersCoding horror - iOS version of a GOTO

Controller Controller

View View

Model Model

Correct Approach on iPadParcel out your controllers

Controller

View

Model

MANDATORY: ALWAYS write/model out your iOS app design before coding!

ViewView

View

ViewView

Controller Controll

er

Controller

Controller

Model

Model

ModelModel

At first, I was like…(in your brain)

But then, it was like…(in the repo)

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

What’s the optimal architecture for a Universal Application?

Non-UI Framework (Networking & Models)

UI Framework (Views & Controllers)

iPhone App iPad App

Optimal Universal App Architecture

Photo Sharing Application

Data from the model is in both the inspector and in the toolbar

MVC Structure

Controller

Controller

Model

Inspector

Toolbar

ChangeUpdate

Change

Update

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

Six Model Options

• Property Lists• Archives• Custom Files• Server/iCloud/APIs• SQLite• CoreData

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

Don’t store data in settings!

• Wrong tool for the job• App may get rejected• Settings Panel test• On/Off Advanced Features

What should you use for quick storage of strings, numbers, arrays, dictionaries, ect?

Property Lists.

What should you use to store partial graphs?

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

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

CoreData again.

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?

Custom Files.

When would you want to use a data archive?

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

What are the two primary features of SQLite?

Provides Database functionality for iOS appsSupports Object Relational Mapping

Know Your Data Model Options

• Property Lists• Archives• Custom Files• Server/iCloud/APIs• SQLite• CoreData

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

What is KVO?

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

objects

Model

Controller Controller

Conclusions• Always start with MVC• Structure your source code for MVC• Don’t fight the framework, understand

what is available & use it• Model out your apps! ***• Understand your data• Use the style guide• Watch all the WWDC videos