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Every project should start with a solid foundation. Find out which pattern is the best for your project.
Making an app is an interesting but lengthy process which can
involve large
groups of designers, developers, project managers, etc. Everything has to run
smoothly in
order to make a well-functioning application, thus you have to start with a good
base. The
first step in developing and shaping the user-friendly interface is choosing a good
app
architecture.
In this article, we are going to focus on iOS App Architecture, but most of the
points are
equally applicable to other platforms.
App architecture essentially presents a set of techniques and patterns which help
developers create a well-structured application.
Mainly, it helps eliminate the possibility of having a nightmare
when trying to implement
additional features or debug some issues. The less code you write, the less chance
there is
of something going wrong, and the app architectures help prevent code duplication,
bad
programming practices, and messy code. This leads to a good base for a healthy code
environment.
So, starting with the basics, here are some questions to bear in mind when choosing
the
right app architecture for a business or a project:
Differentiating between main patterns for iOS such as MVC, MVP, MVVM, and VIPER
could pose
problems to developers. There are some guidelines which you should take into account
when
making a decision.
Before explaining the architectural patterns, basic concepts of Model and View
should be
explained:
The View and the Model never “talk” to each other directly, and the way in which the View is instructed to deal with the Model is what differentiates all these architectural patterns.
In the MVC pattern, the instructions are managed by the
Controller - the layer where all the
wires should be connected. It’s usually least reusable part of the app since it
contains
domain-specific rules. It “owns” the Model and uses it to define the flow of
information.
Think of it as an engine or brain - it decides what happens next.
Problem with MVC (at least in iOS environment) is that ViewControllers, which should
represent a part of the Controller layer, contains partial state and logic of the
View
layer. This usually leads to massive ViewControllers and bulky files.
MVP is an alternative to the MVC pattern where the Controller is
replaced by the Presenter.
In this case, the separation of concerns is as follows:
It’s important to note that MVP uses passive View pattern, which means that all the actions will be forwarded to the Presenter. It will then trigger the UI updates using delegates and the View will only pass actions and listen to the Presenter updates.
The MVVM pattern also allows taking some of this presentation
logic out of the
ViewController.
It introduces View Model - layer that has been described as a state of the data in
the View
- which allows the creation of customized Models for each View.
The idea of MVVM architecture is to have bindings between View and ViewModel which
provide
automatic synchronization of data and visual representation. This helps avoid the
boilerplate code.
View-ViewModel separation is particularly convenient because developers can work on
ViewModel code and designers can work on View in Interface Designer.
The word VIPER is an acronym for View, Interactor, Presenter, Entity, and Routing. This so-called Clean Architecture pattern divides the app’s logical structure into distinct layers of responsibility. Consequently, it is easier to isolate dependencies (e.g. your database) and to test the interactions at the boundaries between layers. VIPER’s distinct layers help deal with this challenge by providing clear locations for application logic and navigation-related code.
Well, let’s see what it boils down to.
MVC results in poor testing process - only Model can be examined, V&C (due to
the
tight connection they have) cannot be tested at all.
The robust connection between Controller and View segments proved to be truly
“unhealthy”
when it comes to software, so a new pattern was developed quickly after.
However, it still is the “starter” pattern, the one that developers mostly begin
with and
improve over time. It should be used for simple and small apps.
Some variations of this simple app design include transition to MVP. Its
added
benefit is that the View is more loosely coupled to the Model and it is easier to
unit test
it because interaction with the View is through an interface.
Both MVC and MVP can be quite clean when implemented correctly, so
this makes
it more of a personal choice.
MVVM’s distribution pattern is better than in MVC, but it is massively
overloaded compared to MVP. Testing is of particular importance here. While
writing
the code you cannot guarantee that
the whole project will function properly; tests help to ensure it will.
MVVM provides
great testing ground.
MVVM should be used for medium-to-large applications and is generally not the
pattern
intended for new developers as it requires a bit more skill to be implemented
correctly.
Nevertheless, it is a great paradigm that stands on its own and is only made better
with a nice binding framework.
The motivation behind MVVM in iOS is that it essentially reduces the complexity of
one’s
view controllers (combating massive view controller syndrome) and makes one’s
presentation
logic easier to test.
This is also the case with VIPER. Its module separation is very beneficial
once it
comes to unit tests, as the great pattern’s distribution lets you test all the
functionalities available.
This architecture is intended for large applications since its benefits are not so
relevant
and noticeable in small apps.
IT Project Manager at K7 Tech Agency
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