200+ IOS Developer Interview Questions and Answers

The output will be 'bye'.

• The code defines a struct 's1Struct' with a property 'abc' initialized to 'Hello'.

• It also has a method 'change()' that changes the value of 'abc' to 'bye'.

• An instance 'a' of 's1Struct' is created and its 'change()' method is called.

• Finally, the value of 'abc' in the instance 'a' is printed, which will be 'bye'.

Questions related to iOS development, including MVC pattern, closures, Google SDK, and managing constraints for labels.

• MVC pattern is a design pattern used in iOS development to separate the application logic into three components: model, view, and controller.

• Closures are self-contained blocks of functionality that can be passed around and used in code. Types include escaping and non-escaping closures.

• Google SDKs like Google Maps provide pre-built functionality for developers...read more

Liskov Substitution Principle focuses on inheritance while Interface Segregation Principle focuses on interfaces.

• Liskov Substitution Principle states that objects of a superclass should be replaceable with objects of its subclasses without affecting the program's correctness.

• Interface Segregation Principle states that a client should not be forced to implement interfaces they do not use.

• Liskov Substitution Principle is related to inheritance hierarchy, while Interface Segrega...read more

The time complexity for finding the longest common prefix in an array of strings is O(n*m), where n is the number of strings and m is the length of the longest string.

• Iterate through the characters of the first string and compare them with the corresponding characters of the other strings.

• The worst-case scenario is when all strings have the same prefix, resulting in O(n*m) time complexity.

• Example: For strings ['apple', 'app', 'apricot'], the longest common prefix is 'ap'.

Classes and structures are both used to define custom data types, but they have some key differences.

• Classes are reference types, while structures are value types.

• Classes support inheritance, while structures do not.

• Classes have deinitializers, while structures do not.

• Classes have reference counting for memory management, while structures do not.

• Classes can have optional property types, while structures cannot.

To upload/download files or fetch requests for API in iOS, you can use URLSession and its related classes.

• Use URLSession to create a URLSessionDataTask for making API requests.

• For file upload, use URLSessionUploadTask and provide the file URL.

• For file download, use URLSessionDownloadTask and specify the destination URL.

• Handle the response and errors using completion handlers.

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

Structs are value types, leading to better performance and memory management in SwiftUI.

• Structs are value types, meaning they are copied when passed around, leading to better performance compared to reference types like classes.

• Structs are immutable by default, making it easier to reason about the state of your app and preventing unexpected changes.

• Structs are more lightweight than classes, which can lead to better memory management in SwiftUI applications.

• Structs are preferr...read more

To integrate Push Notification in iOS, you need to register for remote notifications, handle the registration token, and implement the necessary delegate methods.

• Register for remote notifications using the UIApplication.shared.registerForRemoteNotifications() method.

• Implement the AppDelegate's didRegisterForRemoteNotificationsWithDeviceToken method to handle the registration token.

• Implement the AppDelegate's didReceiveRemoteNotification method to handle incoming notifications...read more

The frame represents the view's position and size in its superview's coordinate system, while the bounds represents the view's position and size in its own coordinate system.

• Frame is relative to the superview, bounds is relative to the view itself

• Frame includes any transformations applied to the view, bounds does not

• Frame's origin is the top-left corner of the view, bounds' origin is always (0,0)

Matrix multiplication involves multiplying rows of the first matrix by columns of the second matrix.

• Matrix multiplication is defined for two matrices A (m x n) and B (n x p).

• The resulting matrix C will have dimensions (m x p).

• Element C[i][j] is calculated as the dot product of the i-th row of A and the j-th column of B.

• Example: For A = [[1, 2], [3, 4]] and B = [[5, 6], [7, 8]], C[0][0] = 1*5 + 2*7 = 19.

Creating views and setting Auto Layout constraints programmatically in a view controller for iOS development.

• Initialize the view: let myView = UIView()

• Set properties: myView.backgroundColor = .blue

• Add the view to the main view: view.addSubview(myView)

• Disable autoresizing mask: myView.translatesAutoresizingMaskIntoConstraints = false

• Set constraints: NSLayoutConstraint.activate([

• myView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),

• myView.trailingAnchor.c...read more

Retain cycle is a memory management issue where objects reference each other and cannot be released. It can be avoided by using weak or unowned references.

• Retain cycle occurs when two or more objects hold strong references to each other.

• To avoid retain cycle, use weak or unowned references instead of strong references.

• Weak references do not increase the reference count of an object and automatically become nil when the object is deallocated.

• Unowned references are similar to w...read more

Swift is a modern programming language while Objective-C is an older language used for iOS development.

• Swift is easier to read and write than Objective-C.

• Swift is faster than Objective-C.

• Objective-C is still used in legacy codebases.

• Swift has a simpler syntax and is more concise.

• Swift has better memory management than Objective-C.

Access controls/modifiers determine the visibility and accessibility of classes, methods, and properties in object-oriented programming.

• public access control allows a class, method, or property to be accessed from anywhere in the code

• open access control allows a class to be subclassed outside of the module where it is defined

• public is commonly used in Swift for most cases, while open is used when you want to allow subclassing from external modules

Automatic Reference Counting (ARC) is a memory management feature in iOS development that automatically manages memory by keeping track of references to objects.

• ARC automatically adds and removes retain/release calls to manage memory for objects.

• It helps prevent memory leaks by deallocating objects when they are no longer needed.

• ARC is the default memory management model in Swift and Objective-C.

• Example: var myObject = MyObject() // ARC automatically retains myObject

• Example: ...read more

Retain, weak, strong, atomic are property attributes in Objective-C for memory management and thread safety.

• Retain: Increases the reference count of an object.

• Weak: Does not increase the reference count, used to avoid retain cycles.

• Strong: Increases the reference count and keeps the object in memory until all references are removed.

• Atomic: Guarantees that the value is always fully retrieved or set in a multi-threaded environment.

Reference types store a reference to the actual data in memory, while value types store the actual data directly.

• Reference types are stored on the heap and passed by reference, while value types are stored on the stack and passed by value.

• Changing the value of a reference type will affect all references to that object, while changing the value of a value type will not affect other instances.

• Examples of reference types in iOS development include classes, while examples of valu...read more

Memory leakage occurs when a program fails to release memory, leading to reduced performance and potential crashes.

• Improper use of strong references in Swift can prevent deallocation of objects, causing leaks.

• Retain cycles occur when two objects hold strong references to each other, preventing memory from being freed.

• Example: A view controller holding a strong reference to a delegate that also holds a strong reference back to the controller.

• Using global variables or singleton...read more

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

Implementing secure app development involves best practices in coding, data handling, and user authentication for both iOS and Android.

• Use HTTPS for all network communications to encrypt data in transit.

• Implement strong authentication methods, such as OAuth or biometric authentication.

• Regularly update libraries and frameworks to patch known vulnerabilities.

• Use secure storage solutions like Keychain on iOS and EncryptedSharedPreferences on Android for sensitive data.

• Conduct re...read more

To create a particular mobile screen, you need to design the layout using Interface Builder or programmatically in Swift.

• Design the UI layout using Interface Builder in Xcode

• Add necessary UI elements like labels, buttons, text fields, etc.

• Customize the appearance using constraints, auto layout, and size classes

• Implement functionality using Swift code to handle user interactions and data processing

Applying SOLID principles improves code maintainability and testability in iOS development.

• S - Single Responsibility Principle: Each class should have one reason to change. Example: Separate User and UserManager classes.

• O - Open/Closed Principle: Classes should be open for extension but closed for modification. Example: Use protocols for new functionalities.

• L - Liskov Substitution Principle: Subtypes must be substitutable for their base types. Example: Ensure subclasses can r...read more

Realm is a mobile database that is faster and easier to use than Core Data.

• Realm is faster than Core Data in terms of performance.

• Realm is easier to use and requires less code for implementation.

• Core Data is more suitable for complex data models and relationships.

• Realm is cross-platform and can be used for both iOS and Android development.

• Core Data is Apple's native framework for data persistence on iOS and macOS.

Property wrappers in Swift are used to add extra functionality to properties.

• Some types of property wrappers include @State, @Binding, @ObservedObject, @EnvironmentObject, @Published, @FetchRequest, @NSManaged, etc.

• Property wrappers help in managing the state of UI components, data flow, and data persistence in iOS apps.

• They provide a convenient way to encapsulate common behavior and logic for properties.

The process involves creating a reference to the Firebase storage, uploading the image data, and handling the completion callback.

• Create a reference to the Firebase storage using FirebaseStorage instance

• Get the reference to the image file using the file path or URI

• Upload the image data to the Firebase storage reference using putFile or putData method

• Handle the completion callback to get the download URL of the uploaded image

Classes are reference types, while structs are value types in Swift.

• Classes are reference types, meaning they are passed by reference, while structs are value types, passed by value.

• Classes support inheritance, while structs do not.

• Classes have deinitializers, while structs do not.

• Classes can have reference counting for memory management, while structs do not.

• Example: class Person {} vs struct Point {}

The UIViewController life cycle consists of several stages that occur when the view controller is loaded and unloaded.

• viewDidLoad() - called when the view controller's view is loaded into memory

• viewWillAppear() - called just before the view appears on the screen

• viewDidAppear() - called just after the view appears on the screen

• viewWillDisappear() - called just before the view disappears from the screen

• viewDidDisappear() - called just after the view disappears from the screen

• de...read more