1. A lighting tour™ to iOS Plus some fun stuff
Victor Wang, Software Engineer & Technical Consultant
November 10, 2016

2. iOS Programming - How to?
How are iOS apps structured?
Model - View - Controller
How are UI components (UIButton, UILabel, UITextField etc.) controlled by code?
View rendering
How to quickly prototype something?
Use storyboards. But it has its own quirks.
How to develop iOS apps modularly
When you want another feature, simply add a module
When you want to deprecate a feature, simply remove that module
MVC, View population cycle, Storyboard

3. iOS Application Structure
Makes extensive use of M (model) V (view) C (controller).
In the context:
M: model (store) that stores reminders
Expose API for get/set
C: controller (ViewController) that controls how data from store is displayed
Call get/set from model -- get data
Use that data to set view
V: view that defines how the UI looks
Expose APIs for set particular components

4. How are UI components controlled by code?
View exposes API
Controller knows about the API and call them
Well-defined and structured in iOS ecosystem
What about something like that ? →
Autolayout
Defines how components should align with each other or relative to edges of screen
Tool: InterfaceBuilder
View Rendering cycle
viewDidLoad
viewWillAppear
viewDidAppear

5. Using Storyboard Best prototyping tool WYSIaWYG
Handles view hierarchy initialisation for you
Although sometimes you may not want it
Save the amount of code you write just to define UI
WYSWYG makes UI debugging easier
Segues
The transition from one VC to another VC
Also takes care of initialising the destination VC
Is also how you pass data to the destination VC

6. iOS APIs
Being a good iOS developer means understanding iOS APIs and the design thinking behind it.
Everything you touched so far is iOS API
View and how views are displayed
UI Components
UI Component properties and methods
Rendering cycle

7. Tackle a ubiquitous VC: UITableViewController
What is delegation
Vital in iOS APIs because they are everywhere, especially in hierarchical views
What is a data source
How iOS design thinking made early version of iOS much smoother than Android
Is also why iOS devices can perform relatively well with way less RAM
A little complex
Tackle a ubiquitous VC: UITableViewController

8. Delegation & Protocol Problem Solution
Sub view is controlled by a controller nested in a parent VC
Sub view wants to
Call a method in parent VC
Pass data to parent VC
Basically: all sort of interactions
Solution
Have sub view own a delegate of parent VC
When parent VC initialise child VC, set child VC’s delegate to itself
Child VC use delegate.”whatever()” to call parent VC’s methods
Another Problem: both child VC and parent VC need to know about these available methods
Child defines a protocol which the parent will implement
A protocol is a set of predefined method headers

9. Put in context
tableView doesn’t know anything about TableViewController
tableView needs information from TableViewController to set its cells
This includes title for the cell, content for the cell
How many cells? How many sections?
Cannot blindly pass all the data to tableView because you create redundant copy
Memory is expensive and very limited resource on iOS devices
iOS defines two protocols
UITableViewDelegate
UITableViewDataSource

10. About memory (RAM) Smart strategy iOS makes to save RAM
TableViewCell - quite a number of them can be based on the same template (a title, some text, maybe adding a button of sorts…)
Why not reuse them?
When tableView is initialised, cell height and screen height is calculated to determine how many cell needs initialising and put in RAM
After that, when cell is scrolled out of visible range (screen) it is recycled and populated with new content to be displayed at the opposite end of screen
Very efficient because the total number of cells stays the same (not overflowing RAM)

11. Extends your app modularly
Very cool 3rd party tool that gives you access to a number of libraries you can use to make your code more concise/readable/fast
Do not take everything because app size is also important. You don’t want user to download an app that’s 500MB with very limited features.
Understand the consequences and always install pods wisely
CocoaPods
Extends your app modularly

12. So many topic to be covered
Web requests
How to open a web page
How to make HTTP requests
GET/POST/PUT
How to handle JSON data
Maps
How to show where the user is
What used to be offered in iOS 2 is an app that retrieves a set of locations of all the coffee shops on campus and use your location to determine which one is the nearest to you
So many topic to be covered
iOS is huge but the it is designed to be understandable (we already covered its core design thinking)