Top 30 iOS Development Interview Questions and Answers 2024

UITableView for displaying data in a list format, UICollectionView for displaying data in a grid or custom layout.

• Use UITableView for displaying data in a list format, such as a contact list or a news feed.

• Use UICollectionView for displaying data in a grid or custom layout, such as a photo gallery or a calendar.

• UITableView is simpler to implement and more efficient for displaying large amounts of data.

• UICollectionView offers more flexibility in terms of layout and customizati...read more

Auto layout is a constraint-based layout system that allows developers to create adaptive user interfaces for different screen sizes and orientations.

• Auto layout helps in creating responsive designs that adjust to different screen sizes and orientations.

• It uses constraints to define the relationship between elements on the screen.

• Auto layout simplifies the process of designing interfaces for multiple devices.

• It allows for dynamic resizing and repositioning of elements based o...read more

I conduct requirement analysis for iOS apps by gathering user needs, defining features, prioritizing requirements, and creating user stories.

• Gather user needs through interviews, surveys, and feedback

• Define features based on user requirements and business goals

• Prioritize requirements based on importance and feasibility

• Create user stories to outline specific functionality and interactions

• Use tools like Jira or Trello to manage and track requirements

Delegates and notification center are key components in iOS development for communication between objects and broadcasting events.

• Delegates are used for one-to-one communication between objects, allowing one object to act on behalf of another.

• Notification center is used for broadcasting events to multiple objects, allowing for loosely coupled communication.

• Delegates are commonly used in UITableView and UICollectionView to handle data and user interactions.

• Notification center ...read more

Best practices for handling memory leaks in iOS development

• Use Instruments to identify memory leaks

• Avoid strong reference cycles with weak or unowned references

• Use autorelease pools for temporary objects

• Implement proper memory management with ARC (Automatic Reference Counting)

MVVM (Model-View-ViewModel) is a design pattern used in Swift to separate the user interface logic from the business logic.

• MVVM divides the code into three main components: Model, View, and ViewModel.

• Model represents the data and business logic of the application.

• View displays the data and interacts with the user.

• ViewModel acts as a mediator between the Model and View, handling the logic for the View.

• MVVM helps in making the code more modular, testable, and maintainable.

iOS life cycle refers to the sequence of events that occur from the time an app is launched until it is terminated.

• App launch: App is launched by user or system.

• Foreground: App is in the foreground and user interacts with it.

• Background: App is running in the background.

• Suspended: App is in the background but not executing code.

• Terminated: App is no longer running.

The bridge between SwiftUI and UIKit is represented by the UIViewRepresentable and UIViewControllerRepresentable protocols.

• UIViewRepresentable and UIViewControllerRepresentable protocols allow SwiftUI views to interact with UIKit views and controllers respectively.

• UIViewRepresentable is used to wrap a UIKit view and make it available to SwiftUI.

• UIViewControllerRepresentable is used to wrap a UIKit view controller and make it available to SwiftUI.

• These protocols enable develop...read more

To integrate pod in project, add pod dependency in Podfile and run pod install command.

• Open Podfile in Xcode project

• Add pod dependency in Podfile

• Run pod install command in terminal

• Open .xcworkspace file instead of .xcodeproj file

GCD and Operation Queue are both used for managing concurrent tasks, but GCD is lower level and more efficient.

• GCD is a C-based API for managing concurrent tasks

• Operation Queue is a higher-level API built on top of GCD

• GCD uses a thread pool to execute tasks, while Operation Queue uses GCD under the hood

• GCD is more efficient for simple tasks, while Operation Queue is better for more complex tasks with dependencies

• GCD is more low-level and requires more manual management, while...read more

Dispatch Queue is a high-level API for managing concurrent operations, while OperationQueue is built on top of Dispatch Queue and adds additional features for managing operation objects.

• Dispatch Queue is a lightweight way to execute tasks serially or concurrently, while OperationQueue is used to manage operation objects that represent tasks.

• OperationQueue allows for dependencies between operations, while Dispatch Queue does not have built-in support for dependencies.

• Dispatch ...read more

CocoaPods is a dependency manager for Swift and Objective-C projects.

• CocoaPods is used to easily manage and install third-party libraries in iOS projects.

• It uses a Podfile to specify project dependencies and automatically downloads and integrates them.

• CocoaPods simplifies the process of adding and updating libraries in Xcode projects.

• Example: 'pod 'Alamofire'' adds the Alamofire networking library to a project.

Dispatch Group is a mechanism in iOS for managing multiple tasks and synchronizing their completion.

• Dispatch Group allows you to monitor a group of tasks and be notified when they are all completed.

• You can use Dispatch Group to wait for multiple asynchronous tasks to finish before proceeding.

• Dispatch Group can be used to manage concurrent tasks and avoid race conditions.

• Example: Using Dispatch Group to download multiple images concurrently and updating UI when all downloads a...read more

Core data stack is a set of classes that work together to manage the model layer of an iOS application.

• Consists of Managed Object Model, Persistent Store Coordinator, and Managed Object Context

• Managed Object Model defines the data model schema

• Persistent Store Coordinator handles interactions with the underlying data store

• Managed Object Context is used to manage the lifecycle of managed objects

ARC stands for Automatic Reference Counting, a memory management system used in iOS development. Retain count is the number of references to an object.

• ARC is a memory management system in iOS that automatically tracks and manages memory usage.

• Retain count is the number of strong references to an object, which determines when the object should be deallocated.

• When an object's retain count reaches 0, it is deallocated from memory to free up resources.

• ARC helps prevent memory lea...read more

Dispatch Queue is a thread-safe way to execute tasks asynchronously, while Operations are a way to encapsulate tasks.

• Dispatch Queue is a high-level API for managing concurrent operations.

• Operations are objects that encapsulate a single task or multiple tasks.

• Dispatch Queue is simpler to use and recommended for most use cases.

• Operations provide more control over task dependencies and cancellation.

• Both can be used together to achieve complex concurrency scenarios.

Steps to add collection view in Swift.

• Create a UICollectionView instance

• Set the delegate and data source of the collection view

• Implement the required methods of UICollectionViewDataSource and UICollectionViewDelegate protocols

• Register the cell class or nib file for the collection view

• Return the number of items and configure the cell in the data source methods

• Implement any additional delegate methods as needed

GCD is a low-level API for managing concurrent operations, while Operation Queue is a higher-level API built on top of GCD.

• GCD is a C-based API for managing queues of tasks, while Operation Queue is an Objective-C class that provides a more object-oriented way to manage tasks.

• GCD is more low-level and requires manual management of queues and tasks, while Operation Queue handles many of these details for you.

• Operation Queue allows you to easily cancel, suspend, and resume oper...read more

App delegate manages app-level events, while scene delegate manages window and scene-level events.

• App delegate is responsible for handling app-level events such as app launch, backgrounding, and termination.

• Scene delegate manages window and scene-level events such as creating and destroying scenes, handling state restoration, and responding to user actions.

• Scene delegate was introduced in iOS 13 to support multiple windows and scenes in an app.

• Both delegates work together to ...read more

Tableview delegate methods are used to customize the behavior and appearance of tableviews in iOS applications.

• Implementing UITableViewDataSource methods like numberOfRowsInSection, cellForRowAt, and heightForRowAt to populate the tableview with data.

• Using UITableViewDelegate methods like didSelectRowAt, heightForHeaderInSection, and heightForFooterInSection to handle user interactions and customize section headers and footers.

• Utilizing methods like willDisplayCell to perform...read more

URL Session using completions is a way to handle network requests in iOS development.

• URL Session is a class in iOS used for making network requests.

• Completions are closures that are called when a network request completes.

• Using completions allows for handling the response data or errors after a network request.

• Example: URLSession.shared.dataTask(with: url) { (data, response, error) in }

iOS manual memory management requires developers to manually allocate and deallocate memory for objects.

• Developers must manually allocate memory for objects using methods like alloc and init.

• Developers must also manually deallocate memory for objects using methods like release.

• Failure to properly manage memory can lead to memory leaks and crashes.

• ARC (Automatic Reference Counting) was introduced in iOS 5 to automate memory management.

• However, manual memory management is still...read more

KVO is used to observe changes in an object's properties, while KVC is used to access an object's properties using a key.

• KVO stands for Key-Value Observing and is used to observe changes in an object's properties.

• KVC stands for Key-Value Coding and is used to access an object's properties using a key.

• KVO is useful for detecting changes in an object's properties and taking action based on those changes.

• KVC is useful for accessing an object's properties in a generic way, withou...read more

Native libraries are pre-compiled code that can be used in iOS apps for various functionalities.

• Native libraries are written in languages like C, C++, and Objective-C.

• They can be used for tasks like image processing, audio and video playback, and networking.

• Examples of native libraries in iOS include Core Data, Core Graphics, and Core Animation.

Model classes in UIKit are used to represent data in an application's user interface.

• Model classes in UIKit typically subclass NSObject and are used to store and manage data for views.

• They can include properties to represent different data fields, methods to manipulate the data, and sometimes protocols for delegation.

• For example, a model class for a user profile in a social media app might have properties like username, bio, and profile picture.

• Model classes are often used in...read more

UITableViews are a type of view in iOS development used to display data in a scrollable list format.

• UITableViews are commonly used in iOS apps to display lists of data, such as contacts, messages, or settings.

• They consist of rows and sections, with each row representing an item of data.

• UITableViews can be customized with different cell types, styles, and layouts.

• They support features like scrolling, selection, editing, and reordering of rows.

• UITableViews are often populated w...read more

Auto layout is a constraint-based layout system used in iOS and macOS development to create user interfaces that adapt to different screen sizes and orientations.

• Auto layout allows developers to create flexible and adaptive user interfaces by defining relationships between UI elements.

• Constraints are used to specify the position and size of UI elements relative to each other or to the parent view.

• Auto layout automatically adjusts the layout of UI elements based on the availab...read more

Data passing between view controllers can be done using properties, delegates, notifications, segues, or user defaults.

• Use properties to directly pass data between view controllers

• Implement delegates to establish communication between view controllers

• Post notifications to broadcast data to multiple view controllers

• Pass data through segues when transitioning between view controllers

• Store data in user defaults for persistent data sharing

Dispatch queue is a queue of tasks that are executed in a first-in, first-out order.

• Dispatch queue is used for managing concurrent tasks in iOS and macOS applications.

• It is a way to manage the execution of tasks in a serial or concurrent manner.

• Tasks can be added to a dispatch queue using dispatch_async() or dispatch_sync() functions.

• Dispatch queue can be either serial or concurrent.

• Serial queue executes tasks in a first-in, first-out order, while concurrent queue executes ta...read more

An iOS developer is responsible for designing and developing applications for Apple's mobile devices.

• Develop and maintain iOS applications using Swift or Objective-C

• Collaborate with cross-functional teams to define, design, and ship new features

• Ensure the performance, quality, and responsiveness of applications

• Stay up-to-date with new technology trends and advancements in iOS development

• Debug and fix issues reported by users

The life cycle of a UIView controller includes methods for initialization, appearance, disappearance, and deallocation.

• ViewDidLoad - called when the view controller's view is loaded into memory

• ViewWillAppear - called before the view is added to the view hierarchy

• ViewDidAppear - called after the view is added to the view hierarchy

• ViewWillDisappear - called before the view is removed from the view hierarchy

• ViewDidDisappear - called after the view is removed from the view hierar...read more