Top Swift interview Questions And Answers for Freshers

1.How we declare variables in Swift ?
 Answer:

Before using constants and variables,we must declare them .

Declare constants with the 'let' keyword and variables with the 'var' keyword.

1.What is difference between 'let' and 'var' declaration ?
​Answer:

let:
We use let keyword to define a constant.It can not be changed afterwards.

 Example:

let Cvalue = 42

A constant value doesn’t need to be known at compile time, but we must assign it a value once.

If you change a constant ,it will give an error as you cannot change the value of a constant.

 Cvalue=58 (It will not compile).

var:

We use  var keyword to define a variable whose value we can easily change.
Example:

var  number1=45
     number1=100;

Now, number1 value is changed to 100.


2.Why we use Type Annotations in Swift ?
Answer:

We provide a type annotation when we declare a constant or variable to identify the kind of values the constant or variable can store.

How to use ?

We write a type annotation by placing a colon after the constant or variable name followed by a space and followed by the type to use

Example:
var Message: String


The Message variable can now be set to any string value without error:
welcomeMessage = "Hello world"

Example of Character Annotation:
let exclamationMark: Character = "!"


3.How to Print Constants and Variables in Swift ?
Answer:

var Stringvalue="india!"
 print(Stringvalue)
 Prints "india!"

Swift uses string interpolation to include the name of a constant or variable as a placeholder in a longer string.

print("The name of my country is \(Stringvalue)")
 Prints "The name of my country is India!"



4.How to use Comments in Swift ?
Answer:
Swift compiler ignores comments  while compiling your code.
Comments in Swift are very similar to comments in C.
Single Line Comment:

// example  of Swift's  single line comment

Multiline comments ( It starts with  (/*) and ends with (*/))

/* this is a multiline comment,
and it's used for multiline texts or codes */

Nested Multiline Comments:

/* starting a  first multiline comment
/* Starting a second nested multiline comment */
 Ending the first multiline comment */

​5.Can you use Semicolon in Swift ?
Answer:
Yes, you can use semicolon in Swift.You don't need to write a semicolon (;) after the end of each statement in Swift.However,it's required if you write multiple separate statements on a single line.
Example:
let myName= "Morgan"; print(myName)

6.How to initialise an empty string in Swift ?
Answer:
var myEmptyString = "" 
How to initialise an empty string using Initialisers?

var MyNewEmptyString = String()


How to find out whether the string is empty ?
if myEmptyString.isEmpty {
    print("Yes ,String is empty")
}
prints "Yes ,String is empty"

7.How to use Mutable String in Swift ?
Answer:
String can be modified (or mutated) by assigning it to a variable.
var myString = "He is a"
newString += " good developer"

newString is now "He is a good developer"'


8.How to get individual characters from a string in Swift ?
Answer:
for char in "iPhone".characters {
print(char)
}

prints
// i
// P
// h
// o
// n
//e

9.What are the value of count1 and count 2 ? 

var iOSArray1 = ["iOS","Xcode","Objective C", "Swift","Cocoa touch"]
var iOSArray2 = iOSArray1
iOSArray2.append("Storyboard")

var count1 = iOSArray1.count
var count2 = iOSArray2.count
Answer: 5,6 

Read:

An Introduction To The Swift Programming Language
Swift 2 Tutorial Part 2: Basics
How to Integrate Google Signin SDK in iOS Application using Swift 
​How To Add  A SWIFT Bridging Header in iOS