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So you are in the process to get an iOS app developed and hire iOS developers but since the architectural design patterns help in the organization or code decluttering, it's crucial for you to choose one which is the most suitable, however, you are unsure about which one out of these architectural patterns would be best suited for your iOS development. Well, to start with Singleton Design Pattern, Decorator Design Pattern, and Bridge Design Pattern, these were the software design patterns first introduced, which could be described as below:

Singleton Design Pattern: Being the simplest of the design patterns, to a single object, it allows the application of one class only.

Decorator Design Pattern: Also known as Wrapper along with the Adaptor pattern, as compared to the Singleton pattern, the Decorator pattern allows the addition of a new function to one existing object.

Bridge Design Pattern: According to Wikipedia, it allows us to, "Decouple an abstraction from its implementation so that the two can vary independently" during the development of an application.

However, these patterns came with numerous concerns of their own including the interaction issues among server and client, business logic and more. And hence, these were followed by newer design patterns for iOS development i.e. MVP, MVC, MVVM and VIPER.

Well, here we have a complete analysis of each one of these architectural design patterns for an ios app. Since the design pattern is the core of any application, this MVP vs MVC vs MVVM vs VIPER Comparison will help you choose better for the long run.

Moreover, another fact that you can't ignore here is that once an application is built without a suitable architectural design pattern just like any house or other building, there are hardly any chances to fix the problems in the future or to modify/improvise it for a better version. So let’s get into a detailed analysis, which includes characteristics, features and the difference between MVP, MVC, MVVM and VIPER in iOS development:

MVC or Model - View - Controller Pattern Architecture in iOS

Model - View - Controller Pattern i.e. also named as MVC design pattern, which was introduced, at first, by Trygve Reenskaug, the Norwegian computer scientist, in the 1970s, basically is a software architectural pattern that is used for the development of user interface (UI). Also, MVC has been found to be the most suited in order to support a simple iOS application by default.

Model:

This central design pattern component includes a data access layer, which further includes business entities such as business logic, business model, databases, and rules in the case of any alterations in the data.

View:

This involves the presentation layer (GUI), which includes displaying the information, for example, a table, bar chart for management, diagram or tabular view for accountants.

Controller:

This involves the interactions or regulation or alterations of the tasks performed by Model and View such as data and displaying of the information, etc.

Moreover, considering an iOS has a very strong View and Controller part connection, the Problem with MVC for iOS is that it gets almost impossible for both of these parts to get tested properly, whereas, the Model part that is separated from the other two parts, can be tested very easily. Moreover, when it comes to its enhanced flexibility, the complex or decoupled codes or their reuse concerns, Model - View - Controller Pattern hasn't been able to provide much of a benefit for iOS.

MVP or Model View Presenter Pattern Architecture in iOS

The MVP or Model - View - Presenter pattern in the iOS app development is a user interface architectural design pattern for iOS, which is made for automated unit testing and improving the SoC (separation of concerns).

Model:

The Model just as mentioned in MVC (Model - View – Controller) includes the data access layer that helps in data defining.

View:

This one involves UIView and UIViewController, moreover, View renders the UI and helps in providing the presenter with the user interactions as a passive interface. It renders the UI

Presenter:

By acting upon and communicating with the Model and View, the Presenter helps in updating the View and data conversion to a format that is UI-friendly.

Moreover, by centralizing the events flow, the Presenter makes it easier to understand how the events occurred and why. It avoids hidden events. In MVP or Model - View - Presenter, on the Model level, the data state in the service is handled and the reuse of the same components is allowed in various different services as well as contexts by the presenter. Other than that, no need for testing is there and the presenter introduces errors using the data state change and logic.

MVVM or Model-View-View Model Pattern Architecture in iOS

MVVM or Model-View-View Model Pattern, which came into existence in 2005 by Microsoft engineers, Ken Cooper and Ted Peters, comes with a union of the View and Controller for forming a view with ViewModel's additional introduction. It is basically MVC's improved version with a better distribution pattern and it separates the UI (user interface) and business logic development. It further facilitates the testing of the app with the use of WPF or Silverlight platforms.

Model:

Being slightly different than in MVP or MVP, the Model involves business as well as validation logic and data. Moreover, it has no dependency on View or ViewModel.

View:

This involves View’s logic, UI's locations, structure as well as the appearance and by communicating with the help of Data Binding, it keeps a check at ViewModel.

View Model:

This involves interaction with View via Data Binding, the state of the View, handling of View’s logic, the transformation of the data that is convenient for the View from Model and the data validation that comes from the View.

Moreover, the MVVM or Model-View-View Model Pattern is better than MVP in the case of the Presentation layer, which isn't at all dependent on the DataBinding and View. And hence, testing becomes a lot easier in this case. However, MVVM is massively overloaded and needs significant resources for memory as compared to the MVP pattern.

VIPER for iOS Development

View, Interactor, Presenter, Entity, and Routing i.e. VIPER for iOS Development, is a design pattern for iOS that works by the division of the app into layers that are distinct and follows a clean approach. VIPER consists of the following parts:

View (V):

View displays the presenter's input and mirrors the actions of the user interface.

Interactor (I):

This involves the business entities, logic and data models.

Presenter (P):

Getting the View's input, the presenter requests, and receives the data to the communicator. However, it doesn’t send any data back to the Entity.

Entity (E):

Entity, which doesn't directly communicate with the presenter, helps in the encapsulation of various types of data. It further involves objects, which the interactor has control over.

Router (R):

Router involves controlling the basic navigation order among screens, the UIWindow objects, UINavigationController, etc.

Apart from that, because of the clean approach and a clear responsibility division in VIPER pattern, there are hardly any issues among the developers. By the introduction of the router layer, it further helps in solving any navigation concerns between screens. Moreover, test-driven development in the case of VIPER gets easier as compared to other design patterns for iOS development.

In the end, although the above-mentioned architectural design patterns for iOS i.e. MVP, MVC, MVVM, and VIPER, are known globally, not every one of them is suitable for all types of projects. And hence, it’s crucial to understand the pros and cons and characteristics of each one of these to find the best-suited architecture design pattern for the development of your iOS app.