Top Swift Interview Questions (2024)

1. What is Swift?

2. What is the difference between Xcode and Swift?

3. What is Tuple in Swift?

4. What are available built in data types in Swift?

5. Is Swift is type safe language?

6. What is Type Inference in Swift?

7. What is the use of optional in Swift?

8. What is the difference between Force Unwrapping Optionals and Implicitly Unwrapped Optionals?

9. What is a Strong Reference in ARC Swift?

10. What is Decision Making in Swift?

11. What is the difference between Array, Set and Dictionary in Swift?

12. What is Subscripts in Swift?

13. What Is Automatic Reference Counting (ARC) in Swift?

14. Is Swift ARC is compile time or runtime?

15. What is the difference between Weak and Strong References in ARC Swift?

16. How to identify device type (OS X or iOS) from Swift?

Q: What is Swift?
Ans:

Swift is a powerful and user-friendly programming language developed by Apple for creating apps for iOS, Mac, Apple TV, and Apple Watch. It is intended to allow developers broader liberty than ever before. Swift is simple to use and open source, so those with a concept can make something amazing.

Q: What is the difference between Xcode and Swift?
Ans:

The distinction between Xcode and Swift would be that Xcode is an Integrated Development Environment (IDE) designed to create iOS and Mac applications, whereas Swift is a programming language used to create iOS and Mac OS applications. Both Xcode and Swift were created by Apple.

Q: What is Tuple in Swift?
Ans:

A tuple type is a list of types separated by commas and contained in parenthesis. A tuple type can be used as a function's return type to allow the function to return a single tuple having multiple values.

Syntax:
var TupleName = (Value1, value2,… any number of values)

Example:
var mulValues = (11, “User 11”)

Q: What are available built in data types in Swift?
Ans:

Following are the available built in data types in Swift-4:

1. Int or UInt
2. Float
3. Double
4. Bool
5. String
6. Character
7. Optional
8. Tuples

Q: Is Swift is type safe language?
Ans:

Swift 4 is a type-safe language, which implies that if a component of your code expects a String, we can't simply provide an Int.

Swift 4 is type-safe, so when we compile code, it conducts type checks and indicates any conflicting types as errors.

var empNo = 21
empNo = "Welcome!"
print(empNo)

--------------
output:
cannot assign value of type 'String' to type 'Int'
empNo = "Welcome!"

Q: What is Type Inference in Swift?
Ans:

Type inference allows a compiler to automatically determine the type of a specific expression when it compiles code by examining the values we provided.

Swift 4 use type inference to determine the correct type.

// type is inferred to be an Int
var iNum = 21
print(iNum)

// type is inferred to be Double
var dNum = 8.654
print(dNum)

-----------------
output:
21
8.654

Q: What is the use of optional in Swift?
Ans:

An optional value helps to write clean code while also making it possible to check for nil values. It can take one of two values: None or Some(T), where T is an associated value of the proper data type supported in Swift 4.

An Optional value is a container of any type (Integer, String,...) that may have a value (1, "Welcome",...) or nil.

let intNum: Int? = 1
let intSecNum: Int? = nil

Q: What is the difference between Force Unwrapping Optionals and Implicitly Unwrapped Optionals?
Ans:

Force unwrapping

It is the process of obtaining the value contained within an Optional. This action is risky since we are asking the compiler to extract the value and assign it to a new variable without seeing whether it is valid or not or nil.

let intNum: Int? = 1
// intSecNum have value 1.
let intSecNum: Int = intNum!

If we force unwrap an Optional item that contains nil, we get a fatalError, the application crashes, and there is no chance of recovering it.

let intNum: Int? = nil
let intSecNum= intNum! // force unwarp - fatal error
------------------------------
output:
fatal error: unexpectedly found nil while unwrapping an Optional value

Implicitly unwrapped optionals

When we write an Implicitly unwrapped optional, we are defining a container that will do a force unwrap every time it is read.

var strGreet: String! = "Welcome"
/* it converts it into plain String as strGreet
automatically unwrapped it's content. */
let userName = strGreet

//assign nil
strGreet = nil
// it will throw fatal error
// fatal error: unexpectedly found nil while unwrapping an Optional value
let user2Name = strGreet

Q: What is a Strong Reference in ARC Swift?
Ans:

Strong references increase the retention rate of the instances (by 1). As long as the object is in use, this prevents Automatic Reference Counting (ARC) from removing it from memory.

Q: What is Decision Making in Swift?
Ans:

The user must provide one or more conditions to be evaluated or verified by the programm when using decision making structures. It is a decision-making statement that allows us to choose different paths depending on a condition (true/false).

Q: What is the difference between Array, Set and Dictionary in Swift?
Ans:

Array

An array is an ordered list of values of the same type. The same value can show up in an array multiple times at different positions.

Set

A set is a collection of distinct values of the same type that has no defined ordering. When the order of the items is unimportant or you need to assure that an item appears just once, you can use a set instead of an array.

Dictionary

A dictionary is a collection with no defined ordering that stores associations between keys of the same type and values of the same type. Each value has a unique key that is provided as an identifier for that value inside the dictionary. Items in a dictionary do not have a defined order, unlike those in an array. A dictionary is used when we have to search up values based on their identifier, similar to how a real-world dictionary is used to look up the definition of a specific word.

Q: What is Subscripts in Swift?
Ans:

Subscripts are used in Classes, Structures, and Enumerations to retrieve values using index from a collection, sequence, or list without invoking a method.

subscript(index: Int) -> Int {
   get {
      // subscript value declarations
   }
   set(newValue) {
      // definitions 
   }
}

Q: What Is Automatic Reference Counting (ARC) in Swift?
Ans:

Swift offers Automatic Reference Counting (ARC) to monitor and manage memory usage of our application. When class instances are no longer required, ARC automatically frees up the memory occupied by those instances.

Q: Is Swift ARC is compile time or runtime?
Ans:

ARC is a compiler feature that allows Objective-C objects' memory to be managed automatically. ARC analyses the lifespan needs of objects and automatically inserts proper memory management calls for programs at compile time, so users don't have to remember when to use retain, release, and autorelease.

Q: What is the difference between Weak and Strong References in ARC Swift?
Ans:

Strong references are the default in Swift, we can use the weak keyword to make a reference weak. A weak reference, unlike a strong reference, has no effect on an instance's retain count. It doesn't hold the object.

Q: How to identify device type (OS X or iOS) from Swift?
Ans:

enum DeviceType {
    case nativeMac
    case iPad
    case iPhone
    case iWatch

    public static var getDeviceTypeName: Self {
        var devieModel = UIDevice.current.model
        #if targetEnvironment(macCatalyst)
        devieModel = "nativeMac"
        #elseif os(watchOS)
        devieModel = "watchOS"
        #endif

        if devieModel.starts(with: "iPhone") {
            return .iPhone
        }
        if devieModel.starts(with: "iPad") {
            return .iPad
        }
        if devieModel.starts(with: "watchOS") {
            return .iWatch
        }
        return .nativeMac
    }
}
-----------------------------------------
//get the device type
print(DeviceType.getDeviceTypeName)