Developing Modern iOS Applications
Mgr. Rastislav Mirek
CEO, TypeSoft
Consultant, Touch4IT
PV239 Mobile Application Development, Faculty of Informatics,
Masaryk University
Organization
Feel free to ask questions anytime.
Breaks?
Have something to add? Differences to Android? Feel free to discuss.
On the following slides ’App’ means Application :)
Outline
1 Introduction
Types of Mobile Applications for Apple Devices
2 Pros and Cons of Being iOS Developer
3 Developing Successful Applications
4 Architecture and Technology Choices
Technology Choices
Architecture
5 Effective Development
6 Summary
Introduction Types of iOS & watchOS Mobile Apps
Types of Mobile Applications for Apple Devices
iOS Apps
both iPhone and iPad or just one device family?
must support all form factors for chosen device family
watchOS Apps - iWatch
need iPhone App for a container
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Introduction Types of iOS & watchOS Mobile Apps
Types of iOS Applications
standard Apps
game Apps (out of lecture scope)
Apps containing App extensions - 20 types e.g.:
Action
Custom Keyboard
Photo Editing
Today (Widgets)
iMessage, Sticker Packs
Call
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Introduction Types of iOS & watchOS Mobile Apps
Today Extension Example
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Introduction Types of iOS & watchOS Mobile Apps
Action Extension Example
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Introduction Types of iOS & watchOS Mobile Apps
Keyboard Extension Example
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Introduction Types of iOS & watchOS Mobile Apps
iMessage Extension Example
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Pros and Cons of Being iOS Developer Cons
Cons of Being iOS Developer
tied to Apple ecosystem
restricted access to device capabilities and APIs
constraints on how should App work (iOS HIG, etc.)
Swift is open source but Objective-C and frameworks are not
XCode
higher development setup costs
App Reviews
detailed, several days
testing for frauds, crashes, usage of private APIs, breaking rules
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Pros and Cons of Being iOS Developer Cons
Requirements for iOS/watchOS Application Developement
Hardware requirements:
Mac computer
Phone or iPad device for testing
Apple Developer account ($99 per year).
Will to explore the unknown and exciting :)
Example
Mac mini 15 490 Kč
iPhone SE 12 990 Kč
approx. 31 000 Kč with Apple Developer account
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Pros and Cons of Being iOS Developer Cons
How to Lower setup costs
computers at the Faculty
XCode simulator
no camera, GPS, some third-party APIs do not work e.g. Facebook
login
second-hand testing devices
short-term device rental
apply for student developer account
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Pros and Cons of Being iOS Developer Pros
Estimated Worldwide Mobile App Downloads Growth
Source: App Annie
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Pros and Cons of Being iOS Developer Pros
Estimated Worldwide Mobile Apps Revenue Growth
Source: App Annie
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Pros and Cons of Being iOS Developer Pros
Estimated US Software Engeneering Salaries in 2016
Source: Stack Overflow
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Pros and Cons of Being iOS Developer Pros
Pros of Being iOS Developer
still fast growing market
strong wave of mobile-first startups ensures future growth
number 1 mobile platform in US
higher income audience, higher revenue, higher salaries
mobile development is growing fast in ČR/SR, resulting in a shortage
of developers
Swift
App Store Environment
excluded content, ranked content (e.g. gambling), granted by Apple
good support, no scam or duplicated apps, rights infringements, etc.
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Pros and Cons of Being iOS Developer Pros
Key Differences to Android
Abstracting from specific technological differences:
users’ behaviour: fewer users, but spending approx. 2x much on Apps
consistent hardware - 8 devices vs. thousands
typically need to support just last 2 iOS versions
these factors result in approx. 30% shorter development time
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Developing Successful Applications
Common Application Success Factors
Apps with native UI have higher success ratio
Startups often aim to deliver too many features in first version
Focus on releasing the first version quickly then iterate frequently
Important Factors
1 App quality (stability, responsiveness) and features
2 Getting on the market early
3 User experience
4 Market Research and Marketing
adding Facebook API to App helps to reduce Facebook Ads cost
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Developing Successful Applications Monetisation
Planning Monetisation
Apple typically has 30% margin. What about Google Play?
1 Paid Apps
fixed price tiers, same price in all countries
2 In-App Purchases (freemium model)
selling via website is possible but it may not be linked from App
3 Subscriptions
4 Auto-Renewable Subscriptions
Apple’s share drops to 15% after first subscription year
5 Apple Pay
real world products only
Apple’s margin is approx. 2%
6 In App Ads: iAds, Facebook Ads, Google Ads, ...
7 Affiliates, B2B (most profitable model)
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Developing Successful Applications Device and iOS Capabilities
Taking Advantage of Device and iOS Capabilities
Touch ID - fingerprint sensor
Force Touch - tap force sensor
SiriKit - voice commands
Search Kit
Health Kit - fitness Apps, health Apps
Push Notifications, Proactive Suggestions (notifications based on user
behaviour patterns)
Accessibility, Dynamic Type, App Extensions, ...
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Developing Successful Applications App Store Release
Releasing to the App Store
Required by App Store
1 support web page
2 screenshots, description, keywords
3 privacy policy in case of App for children
4 age rating
5 export compliance for Apps using cryptography
Common App Refusal Reasons
not possible to report user-generated content in the App
critical bugs, crashes
not complying with HIG, iOS marketing guidelines
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Developing Successful Applications App Store Release
Releasing to the App Store
Beta Testing
via TestFlight (by Apple), Fabric and similar
almost no restrictions on tested Apps
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Architecture & Technology Technology Choices
Native Developement Aternatives
Xamarin C#
React Native Javascript, HTML, CSS
Ionic Angular, Javascript
Advantages and Disadvantages
write once, run everywhere
some components might not be available
another layer between your code and OS - might introduce bugs, lower
performance
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Architecture & Technology Technology Choices
Swift vs. Objective-C
Swift Pros
much newer, modern syntax and features, less verbose, no header files
build with functional programming in mind: Closures (lambda
expressions) are first-class members
has generics, strongly typed language
does not have null pointer
syntax similar to major languages, such as Java or C#
faster development
Objective-C Pros
more stable, Swift changes syntax a little with every major release
still has more libraries
XCode’s support for Swift is still very limited
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Architecture & Technology Technology Choices
Swift vs. Objective-C
Rule of thumb: Use Swift for new projects, Objective-C for legacy projects
already written in it.
Example (Objective-C Method Signature)
+ (NSString *)myMethod:(NSString *)firstArg and:(NSArray
*)secondArg { ... }
Example (Swift Method Signature)
func myMethod(firstArg: String, secondArg: [Int]) -> String {
... }
Swift Demo
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Architecture & Technology Technology Choices
Swift and Objective-C Interoperability
Source: Apple
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Architecture & Technology Technology Choices
Swift’s Most Inovative Feature
First popular language to solve Tony Hoares Billion Dollar Mistake.
Tony Hoare’s Billion Dollar Mistake
“I call it my billion-dollar mistake. It was the invention of the null reference in 1965.
At that time, I was designing the first comprehensive type system for references in an
object-oriented language (ALGOL W).”
Nulls are replaced by explicit optionals that can be chained e.g.
let newOptional = optional?.transformMethod()?.transformMethod()
Optionals are in fact generic enums.
By not force unwrapping them but using if let unwrapped =
optional or guard let unwrapped = optional a lot of errors can be
avoided.
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Architecture & Technology Technology Choices
Swift 2 vs. Swift 3
Highest impact changes:
1 All function parameters have labels unless otherwise specified.
2 Removed for each cycle.
3 Removed ++ and operators.
4 lowerCamelCase for enums and properties.
5 Better import of C functions.
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Architecture & Technology Architecture
App Lifecycle
Source: Apple
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Architecture & Technology Architecture
App Lifecycle
App state changes can be tracked using UIApplicationDelegate’s
methods:
application:willFinishLaunchingWithOptions:
application:didFinishLaunchingWithOptions:
applicationDidBecomeActive:
applicationWillResignActive:
etc.
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Architecture & Technology Architecture
General Architecture Tips
Model-View-Controller:
Keep logic out of both Model and View
Extract logic from controllers to separate services layer
Wrap data persistence into separate layer with API, independent of
persistence technology used
If you are building complex App, split your code into several XCode
projects
Utilise Dynamic Frameworks
Build your own reusable libraries
As your controllers start to grow consider MVVM or VIPER
architecture.
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Architecture & Technology Architecture
Data Persistance
Commonly used persistence technology:
File system
CoreData
Realm
Keychain
NSUserDefaults (in combination with NSKeyedArchiver)
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Architecture & Technology Architecture
Security Aspects of Data Persistance
Application sandbox. Source: Apple
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Architecture & Technology Architecture
Security Aspects of Data Persistance
For security purposes, an iOS app’s interactions with the file system are
limited to the directories inside the app’s sandbox directory.
App typically cannot access data outside of its sandbox.
App’s sandbox is encrypted. Other apps cannot manipulate app’s data.
App can request App Group permission.
Apps in the same group have access to shared sandbox.
They need to have the same group ID.
Useful for app extensions, apps from the same developer, ...
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Architecture & Technology Architecture
Talking to Backend
Common backend choices:
Firebase
Parse
CouldKit
Realm
custom server
Move long running tasks to background threads.
GCD (DispatchQueue) vs. NSOperation/NSOperationQueue
QoS
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Effective Development
Development Tools
Xcode
no good alternatives
limited Swift support
no refractor, no advanced features
unstable code highlighting
works well with storyboards, XIBs, localisation, assets
XCode Instruments
advanced debugging and profiling
CocoaPods
dependency manager for Objective-C and Swift
reliable, standard
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Effective Development Developing User Interface
Auto Layout
Best tool for building UI, offers declarative syntax and visual editor to
replace imperative code.
Adaptive layout - different layout for different screen sizes.
Required vs. optional layout constraints.
Animating Layout Changes
UIView.animate(withDuration: 0.2) {
self.view.layoutIfNeeded()
}
Adaptive Auto Layout Demo
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Effective Development Developing User Interface
Advanced UICollectionView usage
UICollectionView might be the most flexible component of UIKit thanks
to custom layouts.
Custom layouts are not dependent on collection view nor data source.
They extend UICollectionViewLayout.
They can define arbitrary items layout as well as position of
supplementary and decoration views.
If having performance issues override
invalidationContext(forBoundsChange:) and invalidate just the
views that have been repositioned.
Collection view supports interactive layout transitions and layout
animations.
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Effective Development Developing User Interface
Other Development Tips
IB live, reusable views can be created with @IBDesignable and
@IBInspectable.
Interesting blur effect can easily be created with UIVisualEffectView.
There is no performance penalty for concatenating strings in Swift.
Icons, images, string files and data files can easily be organised with
Asset Catalogs and then read in code.
High app download size can be significantly decreased using on
demand resources.
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Effective Development Developing User Interface
Other Development Tips
Work with your designer(s); do not hesitate to tell them if any design
is hard to implement.
There are ready-to-use controllers for camera, image library, email,
sharing, . . .
Consider using Facebook API, Google API, Firebase for: User
tracking, bug reporting, login, notification delivery, etc.
2 things to avoid: Allowing rotation for just for screens of the app and
accessing private APIs or properties (e.g. via KVC).
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Summary
Questions?
Thank you