Swift - if...else if...else Statement

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An if statement can be followed by an optional else if...else statement, which is very useful to test various conditions using a single if...else if statement. Or we can say that if… else if…else statements allow you to check multiple conditions sequentially.

It creates a decision tree where each condition is evaluated in an order and the first true condition’s block of statement will execute. If no condition is true, then the else part will execute. If…else if…else statements are also known as if… else ladder.

When using if, else if, and else statements, there are a few points to keep in mind.

• An if can have zero or one else's and it must come after any else if's.

• An if can have zero to many else if's and they must come before the else.

• Once an else if succeeds, none of the remaining else if's or else's will be tested.

Syntax

Following is the syntax of the if…else if…else statement −

if boolean_expression1{ 
   /* Execute when the boolean expression 1 is true */
}
else if boolean_expression2{
   /*Execute when the boolean expression 2 is true*/
}
else if boolean_expression3{
   /*Execute when the boolean expression 3 is true*/
}else{
   /* Execure when none of the above conditions is true */
}

Flow Diagram

The following flow diagram will show how if…else if…else statement works.

Example

Swift program to demonstrate the use of if… else if…else statement.

import Foundation
var varA:Int = 100;

/* Check the boolean condition using the if statement */
if varA == 20 {

   /* If the condition is true then print the following */
   print("varA is equal to than 20");

} else if varA == 50 {

   /* If the condition is true then print the following */
   print("varA is equal to than 50");

} else {

   /* If the condition is false then print the following */
   print("None of the values is matching");
}

print("Value of variable varA is \(varA)");

Output

It will produce the following output −

None of the values is matching
Value of variable varA is 100

Example

Swift program to check the current season using if…else ladder.

import Foundation

let myMonth = 5

// Checking Season using if...else ladder
if myMonth >= 3 && myMonth <= 5 {
   print("Current Season is Spring")
} else if myMonth >= 6 && myMonth <= 8 {
   print("Current Season is Summer")
} else if myMonth >= 9 && myMonth <= 11 {
   print("Current Season is Autumn")
} else {
   print("Current Season is Winter")
}

Output

It will produce the following output −

Current Season is Spring

Example

Swift program to calculate the grade of the student using if…else if…else statement.

import Foundation

let marks = 89

// Determine the grade of the student
if marks >= 90 {
   print("Grade A")
} else if marks >= 80 {
   print("Grade B")
} else if marks >= 70 {
   print("Grade C")
} else if marks >= 60 {
   print("Grade D")
} else {
   print("Grade F")
}

Output

It will produce the following output −

Grade B