Our new report is live! State of AI for Software Developers Report 2024 Read it now→

Our new report is live! State of AI for Software Developers Report 2024 Read it now→

Advanced Swift Interview Questions for Senior Developers

February 5, 2024


What are advanced Swift interview questions and answers?

Swift (or macOS, iOS, watchOS, tvOS, etc.) is a powerful and automated programming language for Desktop computers, phones, servers, etc. With the help of Swift, the software is made efficiently and seamlessly.

The Swift programming language has quickly become one of the fastest-growing languages in history.

This list of advanced Swift interview questions will help you prepare for your interview, boost your confidence, and increase your chances of landing that iOS Developer job of your dreams!

Create a top-notch Swift resume and get matched with Swift developer roles worldwide without compromising privacy.

Best of luck with your upcoming job interview!


10 Advanced Swift Interview Questions and Answers

1. What is the difference between == and === signs?

The == operator is the equality operator that tests that two things are equal, regardless of the definition of “equal” these things use.

For example, 5 == 5 is true because == means an integer comparison, and the same is true for other built-in value types such as strings, booleans, and doubles.

The === or identity operator compares the identity of objects and checks whether the operands refer to the same object.
Returns false when comparing two references to different object instances, even if the two instances have the same value.

2. How to define a base class in Swift?


Any class that doesn’t inherit from another class is known as a base class.

Swift classes don’t inherit from a universal base class. Classes that you define without specifying a superclass automatically become base classes that you can build on.

Check out the link for detailed information.


3. How can you make a property optional in iOS?

You specify optional chaining by placing a question mark ( ? ) after the optional value that you want to call a property, method, or subscript if the optional is nonzero. This is very similar to putting an exclamation point ( ! ) after an optional value to force its value to open.

4. What is a defer in Swift?


A defer statement is used to execute code just before transferring program control outside the scope where the defer statement appears.

Statements inside the defer statement are executed regardless of how program control is transferred. In other words, a defer statement can be used, for example, to perform manual resource management, such as closing file descriptors, or to perform actions that should occur even if an error is thrown.

5. What are the common factors between struct and class?

In OOP, a class is a blueprint from which individual instances are created.
A class is a blueprint for creating objects (a particular data structure), initial values for state (member variables or attributes), and behavior implementations (member functions or methods).
We define a class using the class keyword.

A struct is similar to a class in definition and instantiation.
We define a struct using the struct keyword.


6. What is trailing closure syntax?

The trailing closure syntax is a little bit of syntactic sugar that makes reading and writing, particularly common code, more enjoyable. Many functions in iOS accept multiple parameters, with the last parameter being a closure.

If the last parameter of a function is a closure, Swift allows you to use a special syntax called trailing closure syntax. Instead of passing your closure as a parameter, you pass it directly after the parenthesized function.


7. What is a good use case for an inout parameter?

inout means that changing the local variable will also change the passed parameters. Without it, the passed parameters will remain at the same value. Try thinking of a reference type when using Inout and a value type without it.

1. A good use case would be the swap function, where it will change the passed parameters.

2. Consider removing the overhead of copying as well. If you have a function that takes a somewhat memory-large value type as an argument (e.g., a large struct type) and returns the same type, and finally, the return of the function is always used only to replace the caller argument, then inout as the associated function parameter is preferable.

8. What is the difference between Self and self in Swift?

When writing protocols and protocol extensions, there is a difference between Self (capital S) and self (lowercase S). When used with a capital S, Self refers to the type that conforms to the protocol, eg. String or Int. When used with a lowercase S, self refers to the value inside that type, e.g. “hello” or 556.

Remember, Self with a capital S refers to any type that conforms to the protocol.
On the other hand, with a lowercase S, self refers to the value the type holds.

9. When do you use strong, weak and unowned references?



Strong references are acceptable in hierarchical relationships where the parent refers to the child, but not the other way around.

In fact, strong references are often the most appropriate reference type.

When two instances are arbitrarily related, make sure one of these instances has a weak reference to the other.

When two instances are related (one instance cannot exist without the other), the instance with the enforced dependency must hold an orphan reference to the other instance.

10. What is Copy on Write (Cow) in Swift?


Copy-on-Write is a computing technique available in the Swift standard library for value types such as collections and structs.

The main idea of COW is to redirect multiple callers to the same resource when they want to access the same resources.
The resource’s state is retained until the caller tries to replace the “copy” of the resource.

If you’re feeling ready for your Swift interview, it’s time to meet a job opportunity that’s right for you!


TalentGrid is a platform used by software developers who are actively looking for jobs, allowing them to share their preferences and salary expectations with employers around the world.

By creating your TalentGrid developer profile, you will have the opportunity to be matched with companies worldwide!

Ready to complete your free profile and find your next role in tech? Sign up today!

Recent Posts

Go to Top