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Switch Case

The control statement that allows us to make a decision from the number of choices is called a switch, or more correctly a switch case-default since these three keywords go together to make up the control statement.

Note*: Switch Case works differently in Swift compared to any other languages :).

Generic Syntax of switch-case Statements:

switch expression
 {
   case expression1  :
      statement(s)
      fallthrough     /* optional */
   case expression2  :
      statement(s)
      fallthrough     /* optional */
  
   default : /* Optional */
      statement(s);
}

fallthrough is used to continue the execution of next cases in switch statements. If you do not write fallthrough then control will be out of switch block.

switch statements can accepts 'integer constants' or 'Character variables'.

What happens during the execution of switch statements ?

Firstly, expression under switch keyword inside the parenthesis is evaluated. Then each case is evaluated one by one unless and until a match is found. If no match is found, the default case is being executed.

Example (Program without fallthrough statement)

import UIKit

var a = 10

switch a {
case 15  :
    print( "Value of index is 15")

case 10  :
    print( "Value of index is  10 ")
   
case 5  :
    print( "Value of index is 5")
   
default :
    print( "default case")
}

Output

Value of index is  10 

Example (Program with fallthrough statement)

/* Copyright @codzify 2017 */
import UIKit

var a = 10

switch a {
case 15  :
    print( "Value of index is 15")
   fallthrough
case 10  :
    print( "Value of index is  10 ")
   fallthrough
case 5  :
    print( "Value of index is 5")
   fallthrough
default :
    print( "default case")
}

Output

Value of index is  10 
Value of index is 5
default case

Example (Program without break statement)

/* Copyright @codzify 2017 */
import UIKit

var i = 2 ;
switch ( i ) 
{
case 1 :
    print ( "I am in case 1 \n" ) ;
   
case 2 :
    print ( "I am in case 2 \n" ) ;
  
case 3 :
    print ( "I am in case 3 \n" ) ;
  
default :
    print ( "I am in default \n" ) ;
  
}

Output

I am in case 2

Example (Program with break statement)

/* Copyright @codzify 2017 */
import UIKit

var i = 2 ;
switch ( i ) 
{
case 1 :
    print ( "I am in case 1 \n" ) ;
    break;
case 2 :
    print ( "I am in case 2 \n" ) ;
    break;
case 3 :
    print ( "I am in case 3 \n" ) ;
    break;
default :
    print ( "I am in default \n" ) ;
    break;
}

Output

I am in case 2

Switch Statements in case of string variables

/* Copyright @codzify 2017 */
import UIKit

var ch:String = "A"

switch ( ch )
{
case "A" :
    print ( "A" ) ;
    fallthrough
case "B" :
    print ( "B" ) ;
   
default :
    print ( "Print Defualt Statements" ) ; }

Output :-

A
B

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