It’s a well-known fact that software architecture in the software industry is critical. It’s important to design the code so that each piece is easily identifiable, has a specific purpose, and fits together with other pieces in a logical manner. It should be easily maintainable, scalable and have high quality. When developing an iOS app, it’s important to think about what iOS project architecture you should use1. Most developers use the pattern suggested by Apple. However, there are others! In this article, we’ll look at VIPER architecture, one of the trending alternatives to MVC that might help you overcome its limitations while keeping your code well-organized, improving your development process.
What is Viper architecture?
VIPER is a backronym for View, Interactor, Presenter, Entity, and Router. This architecture is based on Single Responsibility Principle which leads to a clean architecture, to have a better structure for your iOS project.
Let’s look at what each letter means more in details:
View. The responsibility of the view is to send the user actions to the presenter and show whatever the presenter tells it.
Interactor. This is the backbone of an application as it contains the business logic described by the use cases in the application. The interactor is responsible for fetching data from the model layer, and its implementation is totally independent of the user interface.
Presenter. Its responsibility is to get the data from the interactor on user actions, create a view model instance and carry it to the View to show it.
Entity. It contains basic model objects used by the Interactor. It has part of the responsibilities of the model layer in the other architectures.
Router. It has all navigation logic for describing which screens are to be shown when.
In Viper architecture, each block corresponds to an object with specific tasks, inputs and outputs. It is very similar to workers in an assembly line: once the worker completes its job on an object, the object is passed along to the next worker, until the product is finished.
The connections between the blocks represent the relationship between the objects, and what kind of information they transmit to each other. The communication from one entity to another is given through protocols.
The idea behind this architecture pattern is to isolate your app’s dependencies, balancing the delegation of responsibilities among the entities. Basically, Viper architecture divides your application logic into smaller layers of functionality, each of them with a strict, predefined responsibility. This makes it easier to test the interactions at the boundaries between layers. It fits very well with unit testing and makes your code more reusable.
Key advantages of Viper Architecture
- Simplifies complex projects. Since modules are independent Viper is really good for large teams.
- Makes it scalable. Enable developers to simultaneously work on it as seamlessly as possible
- Decouples the code for reusability and testability
- Divides the application components based on its role
- Sets clear responsibilities, Viper is a champion in distribution of responsibilities
- Makes it easy to add new features
- Makes it easy to write automated tests since your UI logic is separated from the business logic
- It encourages a separation of concerns that make it easier to adopt TDD. The Interactor contains pure logic that is independent of any UI, which makes it easy to drive with tests
- Makes it easy to use
- Creates clear and well-defined interfaces, independent of other modules. This makes it much easier to change the way your interface presents various modules to the user.
- Makes it easier to track issues via crash reports due to the Single Responsibility Principle
- Makes the source code cleaner, more compact and reusable
- Reduces the number of conflicts within the development team
- Applies SOLID principles
- Reduced number of merge conflicts
- You may want to create initial architecture skeleton first and then give modules one by one to other developers to implement logic.
- Makes codebase look similar. Becomes much faster-reading others people code.
Viper architecture has a lot of benefits, but it is important to mention that it is better to use it for big and complex projects. Due to the number of elements involved, this architecture causes an overhead when starting a new small project, so Viper architecture can be an overkill for small projects that do not intend to scale. Therefore for such projects, it is better to use something else, for example, MVVM.
As for the possibility of using Viper architecture in your existing app, in this scenario, consider building a new feature with Viper. This allows you to build a module using Viper architecture and also helps you spot any existing issues that might make it harder to adopt an architecture based on the Single Responsibility Principle.
Viper architecture is a good solution to build working software, iOS app to be proud of!
