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Introduction on Swift coding interview questions

Mastering the landscape of Swift interview questions is essential for leaders and developers venturing into new horizons. For managerial roles, uncover indispensable insights into conducting job interviews. For developers, our article serves as a valuable guide, ushering you through the preparations for the significant day.

As a rule, the core of a top-tier product lies in selecting a superior programming language. This truth resonates profoundly, especially in the realm of renowned brands and their applications. Swift, standing tall among high-quality technologies, exemplifies this fact. Launched in 2014, it signifies a more robust, contemporary, reliable, and user-friendly evolution from its predecessor, Objective C.

In talent acquisition, recruiters persistently seek iOS developers and engineers fluent in the Swift language. However, the journey to interview preparedness can be pretty challenging. To alleviate this pressure, the Factor Dedicated Team has meticulously composed this article, ensuring you are equipped with advanced Swift interview questions and answers, empowering you for a confident stride into your next opportunity.

Swift developer interview questions and answers

To cater to various levels of experience—junior, mid-level, and senior developers—we have organized the questions accordingly. Head to the section that corresponds to the experience level relevant to your project.

IOS Swift basic interview questions for junior developers

Core data interview questions Swift, for starters, include all key aspects. It would be best to have a robust foundation in fundamental concepts and best practices to successfully navigate this dynamic programming landscape. These core data Swift interview questions are tailored specifically for junior developers and designed to empower you with essential knowledge.

Whether you're at the inception of your coding journey or transitioning into Swift from another language, these interview questions IOS Swift serve as invaluable stepping stones. Join us on this exploration.

1. What does iOS Swift refer to?

In June 2014, Apple Inc. unveiled Swift, a revolutionary technology among other programming languages designed to create dynamic applications across mobile and desktop platforms. It stands to reason that with its functional excellence tailored for operating systems such as macOS, iOS, watchOS, and tvOS, Swift seamlessly integrates with the Cocoa framework (Cocoa Touch and Cocoa) and the Objective C library.

What sets Swift apart is its adaptability; it aligns with Apple's expansive ecosystem and extends its capabilities to other operating systems such as FreeBSD, Linux, and Darwin. This versatility positions Swift as more than just a language.

2. What advantages and disadvantages does Swift offer?

Among all existing Swift UI interview questions, this one can be easily explained with videos. We will provide an example below.

This image shows Swift's benefits.

To answer special interview questions IOS developer Swift, let’s compare Swift's unique advantages and disadvantages in the table:

Swift's advantages and disadvantages

Despite these three disadvantages, the underlying trend of Swift is positive, as the perceivable benefits decidedly outweigh the drawbacks.

3. How does iOS Swift handle memory management?

Among IOS developer interview questions, Swift this one is the most ubiquitous.

Swift employs Automatic Reference Counting (ARC) as its memory management mechanism, a concept shared with Objective-C. The process involves tracking strong references to instances of classes (reference types) when assigned or unassigned to constants, properties, and variables. ARC dynamically adjusts the reference count, incrementing or decrementing it based on the interactions with these instances.

The critical role of ARC is evident when instances reach a reference count of zero; at this point, ARC deallocates the memory occupied by those objects, efficiently managing memory resources. It's worth noting that for value types copied upon assignment, ARC doesn't manipulate reference counts.

By default, all references are treated as strong unless explicitly declared otherwise. This intrinsic behavior of Swift's memory management is pivotal in ensuring efficient and effective memory utilization in iOS applications.

4. What does "Optional" in Swift mean?

In Swift, an "Optional" introduces the concept of representing a "lack of value" for any variable type, expanding on Objective C's capabilities. Unlike Objective C, which restricted the "absence of value" to reference types using the unique value "nil," Swift embraces this concept for variable and reference types.

Swift employs "optional" variables to convey the presence or absence of a value, allowing you to declare a variable with a value or as "nil" to signify the absence of a value. This versatility enhances Swift's expressiveness and flexibility in handling various basic data types.

5. How does Swift differ from Objective C?

Difference between Objective C and Swift interview questions is something that is concerning.

Objective-C, essentially an extension of C, incorporates additional object-oriented programming features but carries legacy conventions that complicate coding. Imagine mandatory semicolons at the end of each line and brackets framing Boolean expressions in if/else statements. These elements fail to contribute to the bright side of the development process, don't they?

Now, contrast this with Swift—a language with a much simpler syntax, offering a clean break from the complexities of Objective-C. Objective-C, tethered to C, is limited in its progress, awaiting changes in C before it can evolve.

The clincher lies in how the code is organized. Objective-C scatters your code across two files—a header file (.h) for class definitions and an implementation file (.m) for the actual code.

On the other hand, Swift simplifies matters by consolidating everything into a single .swift file, providing a clearer overview of your work.

With that said, Swift offers a more efficient coding experience. This perspective emerged from the team of developers right from the outset.

6. What sets a "class" apart from a "structure"?

• When utilizing a "class," you gain the advantage of "inheritance," a feature absent in a "structure." The concept of inheritance allows a class to inherit properties and behaviors from another class.
• In the realm of Swift programming, "structures" are categorized as "value types," while "classes" fall under the umbrella of "reference types." This distinction in types further underscores the differences between these constructs.

Let’s continue with other IOS developer Swift interview questions.

7. Which Swift keywords are employed for declaring variables and constants?

Swift developers must declare variables and constants before incorporating them into a program. The "var" keyword facilitates the declaration of variables. The "let" keyword is employed for every temporary constant.

8. What are the "control transfer statements" in Swift?

Swift developers can use a variety of "control transfer statements" that enable the seamless transition of program control from one statement to another, devoid of any conditions. These statements include:

• "break"
• "continue"
• "fallthrough"
• "return"
• "throw".

9. What are "initializers" and "deinitializers" in Swift?

In Swift, "initializers" play a crucial role in executing the 'initialization' process, setting up an initial value for each stored property in a structure, enumeration instance, or class. Swift developers employ the 'init' keyword to utilize "initializers."

Notably, "initializers" in Swift don't return a value. Instead, they effectively initialize new instances of a value type before their first utilization in a program.

In contrast, "deinitializers" operate exclusively on class data types. Swift developers invoke "deinitializers" immediately before deallocating an instance of a class, utilizing the "deinit" keyword.

10. Can you explain Swift's distinctions between "Structures" and "Classes" with an illustrative example?

Swift's differentiation between "Structures" and "Classes" runs deep. A "Structure" or "Struct" functions as a value type, aligning with other basic data types, while a "Class" is a reference type.

A class is a blueprint for crafting a specific data structure, with initial values for remembered variables and member functions.

Consider developing an app to gauge visibility levels on two distinct days, assigning numeric values of "1" and "2" for measurement and comparison. If "Structures" were employed, the code might take the following form:

This image shows an example of code.

In this scenario, the visibility value of "day1.visibility" is set to 1, and "day2.visibility" is assigned a value of 2. As "Day" is structured as a "Structure," the value types are copied by value.

When the statement "var day2 = day1" is executed, it generates a copy of "day1" and assigns it to "day2." Notably, alterations made to "day2" do not impact the values of "day1"; they remain independent.

However, this dynamic would undergo a complete transformation if "Day" were a "Class" instead of a "Structure." In reference types, changes made to "day2" would seamlessly reflect in "day1" and vice versa. The relationship would become bidirectional in this case.

11. Can you explain Swift properties?

In the realm of Swift programming, properties assume a crucial role by categorizing instances into two distinct categories: stored properties and computed properties, each distinguished by its distinctive behavior. When it comes to stored properties, be they variable or immutable, they safeguard values within an instance, ensuring their security. Conversely, computed properties exhibit the remarkable ability to dynamically add values on the fly, eschewing the conventional storage approach in favor of calculated freshness.

• Exploring the intricacies of stored properties: Within the domain of Swift, one encounters stored properties categorized as either variable (distinguished by var) or constant (acknowledged by let). Remarkably, when an unchanging constant is bestowed upon an instance residing in structures, it presents immutability upon the entire entity, stemming from the innate value-type characteristics of structures. Contrarily, variable properties retain their malleability in the realm of classes marked as reference types even when they find themselves assigned to a steadfast constant.
• Exploring computed properties: These intelligent constructs, residing within the realms of classes, structures, and enumerations, take a different path when it comes to value storage. They shun the direct storage of values and instead rely on the wizardry of getters and, occasionally, optional setters to cunningly procure and subtly tweak values. A read-only computed property, housing a solitary getter, dispenses values without the power to accept new ones. Keep an eye out for the var keyword; it's the telltale sign of computed properties that possess the power of mutability.
• Understanding lazy stored properties: Lazy stored properties demonstrate their cleverness by postponing their initialization until that crucial first encounter. This tactical move comes in handy when the initial value hinges on external conditions or involves a taxing, resource-intensive setup. It's worth noting that these specialized properties are exclusive to the world of structs and classes, shunning any association with immutable let variables, and one should tread with caution regarding their thread safety during the initialization process.
• Unpacking property observers: WillSet and didSet are typical property observers. They dynamically respond to changes in property values. willSet comes into play before a value is stored, receiving the new value as a constant parameter (default name is newValue). Conversely, didSet steps in after a value is stored, capturing the old value in a continuous parameter (default name is oldValue). Property observers apply to stored properties, excluding lazy ones, and seamlessly extend to inherited properties through method overriding.

Read more about Swift interview questions Github.

12. Can you explain Swift payments?

Interview questions on Swift payments are asked in the video below. Watch to find answers.

IOS interview questions Swift Medium

Are you considering hiring a mid-level Swift developer? These professionals bring a wealth of experience across various projects, including developing Apple iPhone apps and hands-on Swift work on platforms such as Linux.

Leverage the set of interview questions for IOS developer Swift below. Swift algorithm interview questions are included.

13. How to effectively manage runtime errors in Swift?

Among interview questions for Swift IOS, this one is more practical. Swift provides versatile approaches to handle both runtime and compile time error. Here are a few examples of runtime error handling:

• The Swift "error protocol": Developers can craft a custom "Error" type using an enumeration that conforms to the Swift error protocol.
• The "throws" and "throw" keywords: Integrate the "throws" keyword in the function or initializer definition to propagate errors from the function to the calling code. The "throw" keyword is then employed to throw errors based on the defined error type.
• The "do-catch" block and "try" statement: Functions equipped with the "throws" keyword necessitate a "try" statement since they may encounter errors. This "try" statement is enclosed within a "do-catch" block for effective execution.
• "Try" with a question mark: Swift introduces the option to use "try" with a question mark, i.e., "try?". This results in the return value of the "throwable" function being optional. If the function encounters an error, the value becomes "nil"; otherwise, it holds the wrapped return value of the function.

14. What differentiates "raw values" from "associated values" in Swift enums?

• Raw values are employed to link constants to "enum" cases. Each "enum" case must hold a unique value, as Swift doesn't allow duplicates. To convert the value of an "enum" to its raw value, programmers can use the "rawValue" property. Conversely, a dedicated initializer comes in handy for converting a raw value into an "enum" instance.
• Associated values serve the purpose of attaching data to an "enum" case. These cases can accommodate zero or more such values, and their definitions require a "tuple." This flexibility allows Swift developers to enrich "enum" cases with diverse associated data.

15. What does "optional chaining", “optional binding” mean in Swift?

In Swift, an "optional" can potentially hold a value of "nil." "Optional chaining" empowers developers to inquire about and invoke properties, methods, and subscripts of the optional, even if it contains "nil."

Whether the "optional" holds a value or "nil," calls to properties, methods, and subscripts can be made. In the case of "nil," these calls return a value of "nil."

A notable advantage of "optional chaining" in Swift is its capability to string together multiple queries. If any part of the chain returns "nil," the entire sequence fails. Swift provides effective mechanisms for handling such failures.

16. What are the critical differences between equality and identity operators?

Swift's equality operator (==) examines whether two values are identical. On the other hand, the identity operator (===) checks if two references point to the same instance or occupy the same memory address. Notably, the identity operator yields false when comparing references to distinct object instances, even if these instances share the same value.

17. Can you illustrate the application of inout parameters?

In scenarios where a function deals with a memory-intensive argument and returns the same type, mainly when the function's return value is intended to replace the caller's argument, using inout parameters becomes advantageous. Employing inout signifies that alterations made to the local variable within the function parameter will dynamically modify the corresponding passed parameter.

A practical instance where inout shines is implementing a swap function, showcasing its efficacy in managing memory and maintaining consistency between function parameters and return values.

Swift interview questions for senior developer

Certainly, IOS Swift advanced interview questions delve into more intricate domains. Seasoned Swift developers excel not only in project execution but also showcase proficiency in navigating complex Swift algorithms.

Moreover, their expertise surpasses project delivery, with many capable of actively contributing to the creation of extensive Swift tutorials. This is why Swift experience interview questions in skilled coders cover rare and nuanced aspects.

To know more about IOS developer interview questions for experienced Swift, learn points below.

18. How to ascertain if an integer is a palindrome?

An integer qualifies as a palindrome if it reads the same both backward and forward. For instance, "565" is a palindrome, as it remains unchanged when read backward. However, "-565" doesn't meet the palindrome criteria since it reads as "565-" in reverse.

Here's a code snippet to verify if an integer is a palindrome:

This image shows an example of code.

19. How do you resolve a circular reference in Swift?

Among IOS interview questions Swift for experienced developers, this one is standing tall.

In the realm of Swift, a circular reference unfolds when two instances maintain a strong grip on each other, leading to a memory leak. In such a scenario, neither of the instances undergoes deallocation.

Swift's stringent rules on strong references act as a hurdle, preventing instances from being deallocated in the presence of a strong reference. This results in a situation where each instance clings to the other, rendering deallocation impractical.

To address this circular reference dilemma, developers have the strategic option of substituting one of the strong references with either a "weak" or an "unowned" reference. This tactical adjustment serves as the key to unraveling the intricacies of a circular reference.

20. How to approach iOS app debugging?

Navigating the debugging process is a crucial skill for senior iOS developers, making it a frequent interview topic. Responses to this question may vary, reflecting individual preferences and unique skills that shape each developer's debugging approach.

In essence, outlining a fundamental debugging process forms the basis of a comprehensive response. Highlight essential tools, such as Xcode, which is pivotal in testing and debugging iOS apps. Emphasize your proficiency in setting breakpoints and articulate how this capability enhances the efficiency of iOS app debugging.

Discussing the nuances of debugging across different devices adds depth to your answer. Address variations in debugging strategies, whether working on a computer or an iPhone, to showcase adaptability.

For a more impactful response, cite a specific example from your professional history after presenting the initial overview. This demonstrates your hands-on experience and underscores the practical application of your debugging skills, an invaluable asset beyond theoretical knowledge.

21. Which JSON libraries are compatible with iOS?

iOS does not inherently support the SBJson framework for JSON parsing. Instead, iOS provides its native support for handling JSON through the Foundation framework. The primary classes for JSON handling in iOS are JSONSerialization and Codable protocol.

JSONSerialization is a Foundation class that allows you to convert JSON data to Foundation objects (NSDictionary, NSArray, NSString, etc.) and vice versa. It provides a straightforward way to work with JSON in a native Swift or Objective-C manner.

Final words on interview questions in Swift

Best of luck in your iOS Swift interview preparation!

The iOS interview questions Swift provided above are a valuable tool to assess a candidate's skills during the interview process. They enable you to gauge how well a potential coder comprehends the multiple parameters of this object-oriented programming language.

For those seeking a secure onboarding process for Swift developers, free from conducting interviews and individual vetting, consider reaching out to the Factor Dedicated Team.

Our developers undergo thorough, continuous performance monitoring throughout the entire project. You will be connected exclusively with the most suitable candidates possessing industry-specific experience. With the Factor Dedicated Team standing behind their work, we offer a risk-free solution to ensure the success of your business. Let's connect!

Frequently Asked Questions

How to prepare for iOS Swift interview?

Preparing for an iOS Swift interview requires a strategic approach to showcase your skills and depth of understanding. Here are some critical steps to ensure you're ready for the challenge:

• Solid understanding of Swift: Ensure you possess a robust understanding of Swift programming language features, iOS app architecture, and design patterns.
• Project discussion: Be prepared to discuss the projects you've worked on, emphasizing your role, challenges faced, and solutions implemented.
• Stay updated on Swift: Familiarize yourself with Swift's latest features, enhancements, and best practices to demonstrate your commitment to staying current with industry trends.
• Coding practice: Practice coding exercises related to Swift and iOS development. Platforms like LeetCode and HackerRank offer a wealth of challenges that can help sharpen your skills in correct code.
• User interface and experience: Be ready to discuss how you approach creating user-friendly interfaces and optimizing the user experience within the context of iOS development.
• Version control and collaboration: Familiarize yourself with version control systems, especially Git, and emphasize your experience in integrated development environment.
• Testing and debugging proficiency: Highlight your proficiency in testing and debugging iOS applications. Discuss your approach to unit testing, UI testing, and troubleshooting common issues. Showcase instances where your testing strategies contributed to the app's overall quality.

What is protocol in Swift interview questions?

This inquiry is one of the most common Swift programming interview questions. Think of a protocol oriented programming as a set of rules defining the methods and properties a type should have. It's like a contract for functionality without dictating how it's done. Different types, such as classes or structures, can adopt these protocols, promising to follow the specified guidelines.

This promotes consistency in code and allows for versatile, reusable components, making Swift applications more modular and maintainable.

Protocol oriented programming Swift interview questions are a must to estimate the developer's level.

What is the basic concept of Swift?

At the heart of its existence, Swift encapsulates the soul of developing dependable applications across the diverse spectrum of Apple's platforms. This vibrant and dynamic programming language seamlessly intertwines potency with a design ethos centered around user-friendliness, proudly showcasing attributes such as type safety, versatile options, and automated memory management features. Swift's syntax, designed with attention, emphasizes clarity and user-centric experiences.

Accommodating both procedural and object-oriented programming paradigms, Swift amplifies its adaptability, becoming a helpful technology across various application development scenarios. In its ultimate form, Swift serves as the catalyst, propelling developers through a streamlined journey, reinforcing code security, and bestowing the power to create high-performance applications that transcend across iOS, macOS, watchOS, and tvOS platforms.

IOS interview questions for experienced Swift developers should focus on matters.

What type of coding questions are asked in interviews?

Coding questions in interviews cover various topics, ensuring a comprehensive assessment of a candidate's programming capabilities. Here's a more detailed breakdown of the domains explored:

• Algorithmic challenges: Candidates may encounter problems that require the application of common algorithms like sorting, searching, and dynamic programming. The focus is on problem-solving skills and algorithmic efficiency.
• Data type structures: Swift data structures interview questions may involve effectively using different data structures such as arrays, linked lists, queues, stacks, and hash tables. Candidates are expected to choose the most suitable data structure for specific scenarios.
• Manipulation of arrays: Tasks may include array manipulations, such as reversing, rotating, or transforming arrays to achieve specific outcomes. This assesses a candidate's ability to work with fundamental data structures.
• Searching and sorting: Evaluation of a candidate's proficiency in implementing and optimizing searching and sorting algorithms like binary search, quicksort, or mergesort.
• Dynamic async and sync programming: Assessing a candidate's understanding of dynamic programming concepts and their ability to work with both asynchronous and synchronous programming paradigms.
• Graph problems: Candidates may be presented with problems related to graph theory, including tasks like traversals (depth-first or breadth-first), finding paths, or identifying graph cycles.
• Bit manipulation: Testing knowledge and proficiency in manipulating individual bits within binary numbers. This is particularly important in scenarios where memory efficiency is critical.
• Traversal of trees: Questions may involve traversing different types of trees, such as binary trees, AVL trees, or Red-Black trees. This assesses a candidate's understanding of tree structures.
• System design: Candidates may be asked to design scalable and efficient systems, considering factors such as performance, scalability, and reliability. This often involves discussing trade-offs and making architectural decisions.
• Concurrency and multithreading: Evaluating a candidate's ability to manage concurrent processes and use multithreading effectively, considering issues like race conditions and synchronization.
• Database queries: Examining a candidate's proficiency in writing complex SQL queries and optimizing database interactions. This may include tasks related to data retrieval, modification, and joining.

These diverse coding challenges provide interviewers with insights into a candidate's problem-solving approach, algorithmic thinking, and practical programming skills across various domains essential for software development. Candidates must demonstrate adaptability and creativity in addressing problems within these diverse areas. IOS Swift interview programming questions are relevant.

How to prepare for iOS interview?

Prepare for an interview questions Swift with a focused approach:

• Understand MVC architecture, delegates, protocols, and Swift programming language features.
• Highlight key iOS projects, emphasizing problem-solving and your role.
• Demonstrate clean Swift code with a strong understanding of language features.
• Know iOS apps lifecycle methods and app state management.
• Familiarity with Interface Builder and Auto Layout for responsive UIs.
• Showcase API call skills using URLSession or third-party libraries.
• Understand Core Data for data persistence in iOS apps.
• Proficiency in managing concurrency with GCD.
• Strong understanding of UIKit components for UI development.
• Knowledge of XCTest for unit testing and UI testing.
• Git proficiency for version control.
• Familiarity with App Store guidelines and common rejection reasons.
• Keep abreast of iOS trends, SwiftUI, Combine, and recent updates.
• Prepare for behavioral questions with examples from your experience.
• Practice coding problems with programming languages and conduct mock interviews for skill refinement.

Preparation on all points above will be immensely beneficial when you have to answer Swift technical interview questions.