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Swift · Question Set
Design Patterns & Architecture in Swift interview questions for placements and exams.
Questions
12
Included in this set
Subject
Swift
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Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for Swift.
The Coordinator pattern moves navigation logic out of view controllers into coordinator objects, improving separation of concerns, testability and reusability of navigation flows. It is increasingly referenced in Swift architectural discussions.
For complete preparation, combine this set with full subject-wise practice for Swift. You can also explore other subjects and sets from the links below.
When deciding the architecture of a new Swift module, you start by analysing complexity, team size, scalability and testability requirements. /n/n If the module handles UI, network, caching and testing, a layered architecture such as Clean Architecture may be a strong choice: you define a Domain layer containing business logic and use cases, a Data layer managing networking and caching repositories, and a Presentation layer with ViewModels and Views (e.g., SwiftUI or UIKit). You ensure dependencies go inward (Presentation depends on Domain, Domain depends on Data) and inject dependencies via constructor injection. Navigation may be managed by a Coordinator. /n/n This setup improves testability (you can mock data repositories), maintainability (clear layer boundaries), and scalability (you can swap caching strategies or network implementations without touching UI). Explaining this in an interview demonstrates depth of architecture knowledge.
The Model-View-Controller (MVC) pattern divides an application into three main components: the Model (manages data), the View (presents data), and the Controller (mediates between Model and View). It is a classic architecture used widely in iOS development and forms a foundation for more advanced patterns. (Ref: design patterns for Swift)
In MVVM the ViewModel sits between the Model and View, handling business logic and exposing data in a format the View can display. This separation allows independent testing of the ViewModel, cleaner UI code and improved maintainability. It is widely adopted in Swift interview discussions.
The Singleton pattern restricts instantiation of a class to one object and provides a global point of access to that object. In Swift this is often used for shared managers or services. It’s a fundamental candidate for interview questions about design patterns in Swift.
The Factory Method defines an interface for creating an object, but lets subclasses decide which class to instantiate. This decouples the code that uses objects from the concrete classes. It is a key creational pattern in Swift architecture discussions.
Dependency injection means providing a class its dependencies rather than having the class create them. This reduces coupling, improves testability and aligns with clean architecture principles in Swift. This topic often appears in architecture interview questions.
Clean Architecture proposes a separation into layers such as Domain (business logic), Data (repositories), and Presentation (UI), so that high-level policies don’t depend on low-level implementations. In Swift this architecture is increasingly used in large apps and shows up as an advanced interview topic.
The Observer pattern defines a one-to-many dependency so that when one object changes state, its dependents are notified. In Swift this is often implemented via NotificationCenter or Combine’s publishers/subscribers. Knowledge of this pattern is expected in iOS/Swift interviews.
MVC is simple and easy to understand: Controllers mediate between UI and data. Its chief disadvantage in iOS is that ViewControllers often become 'massive view controllers'. /n/n MVVM improves separation: ViewModels handle logic and provide data to Views, improving testability; however you may need binding or reactive frameworks. /n/n VIPER pushes layering further: you have View, Interactor, Presenter, Entity, Router; this maximises modularity and testability but introduces more boilerplate. /n/n You may prefer MVC for simple apps or prototypes, MVVM for moderate complexity apps with test requirements, and VIPER or Clean Architecture for large, scalable enterprise apps with many modules and teams.
Common anti-patterns in Swift apps include Massive View Controllers (controllers that do both UI and business logic), Tight Coupling (classes deeply dependent on each other), God Objects (single objects doing too much). /n/n To refactor: extract business logic into ViewModels or Interactors, apply Dependency Injection to reduce coupling, implement Coordinator pattern to handle navigation, break modules into smaller features, adopt Clean Architecture layering to separate concerns. Explaining this shows you understand not just good patterns but also how to avoid bad design.
Design patterns and architectures provide structure, modularity and reuse but come with trade-offs. /n/n Adding many layers (Clean Architecture) improves testability and modularity but increases boilerplate, slows initial development and may over-engineer simple features. Heavy use of patterns can reduce clarity if misapplied. /n/n In real-world Swift projects you balance by applying simpler patterns for small modules and reserving heavy architectures for complex or long-lived modules. Always favour readability, maintainability and team familiarity. Explaining this in interview shows practical judgement beyond textbooks.