Modern iOS Application
Development
Rastislav Mirek
UIKit Demo
How did you like it?
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.

• Alternatives: E.g. Async Display Kit
SwiftUI Demo
What are advantages of Storyboards
and what are advantages of SwiftUI?
UIKit vs. Swift UI
UIKit SwiftUI
MVC Reactive, MVVM
Has UICollectionView No UICollectionView
More mature, well known New, modern & “hot”
More visual, navigation visualization Hot reloading, multiple previews
Only targeting one platform One UI for iOS, Mac an Apple Watch
Better tooling, more 3rd party libraries Code only, no “black box” storyboard
code
Classes & Inheritance Structs & Composition
Wide OS version support One iOS 13
Still dominant Great for new apps
Swift
First popular language to solve Tony Hoares 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.
Swift’s Most Inovative Feature
What do you think is a biggest gain of not
having implicit nulls? Can you quantify it?
Swift Key Characteristics
• Verbose: All function parameters have labels unless
otherwise specified.

• Functional as well as imperative.

• Modern features: Optionals, custom operators, imutability,
extensions on protocols, minimalistic syntax, enums with
associated values, code in unicode, ...

• What you would expect: Generics, exceptions, functional
methods (map, reduce, ...), structs, inheritance, …

• Stable, fast, open source
iOS App Architecture
App Lifecycle
Architecture Tips
• Model-View-Controller (only for UIKit):

• 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.
Persistance
How do you plan to persist
data for your projects?
Local Data Persistance
Commonly used local persistence technology: 

• File system

• CoreData

• Realm

• Keychain

• UserDefaults (in combination with serializers)
App Container
Backend & Remote
Persistence
Common backend choices:

• Firebase 

• CouldKit 

• Realm 

• Custom server

Move long running tasks to background threads.

• GCD (DispatchQueue)

• OperationQueue
Development Tips
Development Tools
• Xcode

• no good alternatives

• works well with storyboards, XIBs, localisation, assets

• XCode Instruments

• advanced debugging and profiling, some pretty cool

• Dependency Managers

• Swift Package Manager (SPM)

• CocoaPods

• Carthage
What would you do to make your
mobile app stand out from the crowd?
Any cool tech/visual things planned
for your projects?
UICollectionView
• 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.
Tips
• Consider using Facebook API, Google API, Firebase for: User
tracking, bug reporting, login, notification delivery, etc.

• Work with your designer(s); do not hesitate to tell them if any
design is hard to implement.

• 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.

• Multiproject XCode workspaces 

• There are ready-to-use controllers for camera, image
library, email, sharing, . . .

• 2 things to avoid: Allowing rotation for just some screens
of the app and accessing private APIs or properties.
Questions?
Thank you