Beginner Level Swift Interview Questions:
1. What is Swift?
Answer:
Swift is a powerful, open-source, general-purpose programming language developed by Apple, designed for building applications for iOS, macOS, watchOS, and tvOS. It’s known for its ease of use, performance, and safety features, making it a popular choice for developers.
2. What are Variables and Constants in Swift?
Answer:
Variables (var) can change their value over time, while constants (let) stay the same after you assign them once.
Example:
You can change name, but not birthYear. Using let helps make your code safer and easier to understand.
3. What is Optionals in Swift?
Answer:
An Optional is a type that can hold either a value or nil (no value). It’s Swift’s way of handling the possibility of “no value” safely.
Example:
Using ? means middleName might contain a string, or it might be nil. You can safely unwrap it using if let or guard.
4. What is type inference?
Answer:
Swift can figure out (or infer) the type of a variable based on the value you assign. So, you don’t always need to explicitly mention the type.
Example:
let age = 25 // Swift knows this is an Int
This helps keep your code clean and readable.
5. What are functions in Swift?
Answer:
Functions are reusable blocks of code that perform a specific task.
Example:
You can call this function with a name, and it will print a greeting. Functions help organize code better.
6. What is a Tuple in Swift?
Answer:
A Tuple lets you group multiple values into one compound value.
Example:
Useful for returning multiple values from a function.
7. What are Arrays in Swift?
Answer:
Arrays are ordered collections that hold multiple values of the same type.
Example:
var fruits = [“Apple”, “Banana”, “Mango”]
You can access elements by index, like fruits[0] which gives you "Apple".
8. What is a Dictionary in Swift?
Answer:
A Dictionary stores data in key-value pairs.
Example:
It’s great for quick lookups using keys.
9. What is a Loop in Swift?
Answer:
Loops are used to repeat a block of code multiple times. Common loops: for, while, and repeat-while.
Example:
This prints 1 to 3.
10. What is String Interpolation?
Answer:
String interpolation lets you insert variables into strings using \(variableName) syntax.
Example:
Intermediate-Level Swift Interview Questions
1. What is the difference between struct and class in Swift?
Answer:
Both struct and class let you define custom data types, but they have key differences:
- Structs are value types, meaning when you assign them to a new variable, they’re copied.
- Classes are reference types, so changes made in one place are reflected everywhere.
Also, only classes support inheritance.
2. What is a protocol in Swift?
Answer:
A protocol is like a contract that defines what methods or properties a type must implement. in other words we can it’s same like interface in java
Example:
3. What is optional binding?
Answer:
Optional binding lets you safely unwrap an optional if it contains a value. You usually do this using if let or guard let.
Example:
This prevents crashing from force-unwrapping a nil value.
4. What is the difference between weak, strong, and unowned references?
Answer:
strongis the default and keeps the object alive.weakdoesn’t keep a strong hold, and is used to avoid retain cycles.- It becomes
nilwhen the object is deallocated.unownedis likeweakbut doesn’t becomenil—you must be sure the object will still exist.
Used mostly in closures and delegate patterns.
5. What is a closure in Swift?
Answer:
A closure is a block of code you can pass around and execute later. Think of it like a function without a name.
Example:
Closures are heavily used in asynchronous code and animations.
6. What is the difference between map, filter, and reduce in Swift?
Answer:
maptransforms each element in a collection.filterremoves items that don’t match a condition.- reduce combines all items into a single value.
Example:
7. How does error handling work in Swift?
Answer:
Swift uses do, try, and catch for error handling. You define errors using enum and throw them using throw.
Example:
This helps make your code predictable and safer.
8. What is guard in Swift and why is it useful?
Answer:guard is used to exit early from a function if certain conditions aren’t met. It improves readability by handling invalid conditions upfront.
Example:
9. What is a computed property?
Answer:
A computed property calculates its value rather than storing it. It has a get (and optionally a set) block.
Example:
It updates automatically based on other data.
10. What is the difference between synchronous and asynchronous code?
Answer:
- Synchronous code runs in order, line by line, and waits for each task to finish.
- Asynchronous code lets your app continue running while waiting for a task (like a network call) to finish. It uses closures,
async/await, or completion handlers.
Also Read : Advanced Swift Interview Questions
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