Mobile iOS Application Architectures

iOS Application Architectures
Arpit Kulshrestha

Type of Client Applications
Thin Web Client
Every communication
will be done with a
central processing server
,Client only used to show
that processed data in
mannered way to
accomplish information
to end user using that
application.
Thick Client
Unlike thin clients, thick
clients do not rely on a
central processing server
because the processing
is done locally on the
user system. This will
provide users with more
features, graphics and
choices making the
applications more
customizable
Smart / Rich Client
Smart clients are
Internet-connected
devices that allows a
user's local applications
to interact with server-
based applications
through the use of web
services.

Why Good Architecture Required
Distribution
Easiest way to defeat
complexity is to divide
responsibilities among
multiple entities
following the Singleton,
layers , design patterns
etc.
Scalability
A application can grow
to a large level and may
change the requirements
at mid level or last phase
of development so it
must be scalable.
Ease of
Development
Less and Smart code
which would not take too
much time as well as
should not too complex
to implement and
understanding.

Design Patterns in iOS
● Singleton
● Delegation
● Observer (KVO , NSNotification )
● Facade Design
● Template Method
● Composite

Singleton
● When a class is restricted to just one instantiation, that one object is called
a singleton
● It is a very common pattern, but developers have to be careful not to
overuse it.
Delegation
● As the name indicates, the delegation pattern is used to have one object
delegate control to another object to act on its behalf.
● This is used to keep implementation specific behavior out of the generic
class

Key Value Observer
● The observer pattern is used when one object wants to know when another
object changes
● This pattern is build into every NSObject vi Key-Value Observing
NSNotification Centre
● NSNotificationCenter provides a centralized hub through which any part of
an application may notify and be notified of changes from any other part of
the application

Facade Design
● Alamofire , AFNetworking, Kingfisher etc.
● Facade Design patterns provide simple interface of large and complex
structure / algorithm / calculations.
● We should use in our architecture to separate out complex things with
simple to use interface.
Template Methods - Subclassing
● For usability of features in applications we can make those classes with
some basic functionality which can be subclassed by other node class to
extend the functionality.

Layers in
Architectures
Single Unit of Architecture
Layer is a basic unit of Architecture
to distribute responsibility of
features.
Number of layers and their
responsibilities could be differ as
per requirements.
It usually between user interactions
points to Network / DB layers and
vice versa too.

A Sample Layered Architecture
UI Layer Validation Layer
Authentication
Layer
Encryption
Layer
Storage
Layer
Payment
LayerBookMark Layer

Architectural Use Case Problem for Discussion
There is requirments of iOS Project, where every text label content’s color, font
name, text is configurable from Server at any point of time even after app
upload to Apple Store. Some features of this app could be offline too and
others are heavily dependent upon Server API data.
What Architectural Approach you will take to fulfill above Criteria?

Data Model Layer
● API Request data Model
● API Response Data Model
● Application Data Model
● Business Data Model
These Both can be combined, Not
necessary to be different unless
too big Architecture and data to be
handled.

Application Data Model Vs Business Data Model
UI Layer Network Layer
Request data Model
Storage Layer
Application Data Model
Business Data Model
Contains - Cache, internal calculation use, ViewModel etc.

You can use Json Export for Data Model
{
username : “john”,
Email : “john@matellio.com”
First_Name : John,
Lastname : mishel,
Age : “30”,
Token : “73783e8w798”
sessionKey : “heiudh37897weq”
}
Name - John Mishel
Email - john@matellio.com
Age - 30

Assembly Layer
● It contains app configuration level informations such as urls, 3rd party keys,
base classes of (viewcontroller - navigation - UI component) etc.
● Appdelegate , UIApplication subclass , plist configurations, theme , font ,
color , image configurations of iOS project.
● Application level declarations, App Global Cache, and information which
would be affecting and related to complete application.

Infrastructure Layer
Infrastructure Layer Contains :-
■ Helper Classes
■ Extensions / Category
■ App Utility
■ Interface / UI Utility

Services Layer
● Whenever our app required to communicate with the external systems,
services whose data and authentication required to achieve features.
● When interacting with Network , Server API. (Alamofire handling, Error
Handling)
● 3rd Part API Implementations. (Facebook, Twitter , pubnub etc)

Storage Layer
Storage Layer in iOS Contains :-
● Core Data / Realm Implementations
● Sqlite Implementations
● Save data in plist / json file / other files in document directory only for
non incremental data.
Note :- Writing data to files would be a costlier comparing to DB in terms of CPU
processing.

Manager Layer
● When a major process, complex calculations, hardware processing,
application module processing required to be managed as Single
responsibility then it would count in Manager Layer.
● Geo Location, BLE handling , Beacon handling, Remote Notification ,
Encryption handling, Address Book Manager, Media Cropping handling, user
credential handling (via keychain, user defaults etc.), I/O file operations etc.

Coordinators Layer
● Not always necessary to be in separate layer.
● To combine and coordinating chain of features / asynchronous callbacks /
event triggering success or failure.
● There should be very less / No processing in terms of CPU uses.
● Validation Manager, message passing between multiple module, controllers,
converting one form of data to another, synchronize data from multiple
sources, combine business logic.

Architectural Use Case Problem II for
DiscussionThere is a Ecommerce iOS Application, User can browse the app even without login.
- Requirements contains - category , subcategory and featured items in every sub category should
be configured from server and dynamic (Not changes frequently but may change in 15 days)
- There should be some featured items in each category / subcategory which should show as fast
as possible even in low network, there should be no delay due to any circumstances.
- Server team comes up with 14 API to call for all such data (category , subcategory and featured
items with images) , and data could be change in future.
- During testing, client observed that After App Download, some time server fails and no data
(category , subcategory and featured items) is there only blank screens.
- Client thoughts it would give a very bad impression if after download there will be blank screens
even due to any reason. User will be able to see at least category - subcategory and featured
items with images in any condition. Analyse and Give Suggestions

UI Layer
UI Layer Contains :-
● Views
● ViewController
● ViewModels
Type of Architecture Methodology with above sublayers :-
● MVC
● MVP
● MVVM
● Clean Architecture

MVC
Usually used for Small Application,
those initial development time could
be upto 3-4 month other than
maintenance.
MVP
Majorly not practical use, almost
similar to mvp other than unit
testing configurability have more
significance here.
MVVM
Most popular, Significant Mid - Large level
application (development time 5 - 12 month)
other than maintenance.
VIPER
Complex, Very large, Scientific &
Research, Enterprise application
(development time 1.5 year to 3 year)
other than maintenance.

Mobile iOS Application Architectures

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