Swift - Switch Statement


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A switch statement in Swift 4 completes its execution as soon as the first matching case is completed instead of falling through the bottom of subsequent cases like it happens in C and C++ programing languages. Following is a generic syntax of switch statement in C and C++ −

switch(expression){
   case constant-expression :
      statement(s);
      break; /* optional */
   case constant-expression :
      statement(s);
      break; /* optional */

   /* you can have any number of case statements */
   default : /* Optional */
      statement(s);
}

Here we need to use break statement to come out of a case statement otherwise execution control will fall through the subsequent case statements available below to matching case statement.

Syntax

Following is a generic syntax of switch statement available in Swift 4 −

switch expression {
   case expression1 :
      statement(s)
      fallthrough /* optional */
   case expression2, expression3 :
      statement(s)
      fallthrough /* optional */
   default : /* Optional */
      statement(s);
}

If we do not use fallthrough statement, then the program will come out of switch statement after executing the matching case statement. We will take the following two examples to make its functionality clear.

Example 1

Following is an example of switch statement in Swift 4 programming without using fallthrough −

var index = 10

switch index {
   case 100 :
      print( "Value of index is 100")
   case 10,15 :
      print( "Value of index is either 10 or 15")
   case 5 :
      print( "Value of index is 5")
   default :
      print( "default case")
}

When the above code is compiled and executed, it produces the following result −

Value of index is either 10 or 15

Example 2

Following is an example of switch statement in Swift 4 programming with fallthrough −

var index = 10

switch index {
   case 100 :
      print( "Value of index is 100")
      fallthrough
   case 10,15 :
      print( "Value of index is either 10 or 15")
      fallthrough
   case 5 :
      print( "Value of index is 5")
   default :
      print( "default case")
}

When the above code is compiled and executed, it produces the following result −

Value of index is either 10 or 15
Value of index is 5
swift_decision_making.htm
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