An if-else statement allows you to execute different blocks of code according to the given expression. If the given condition is true, then the code present inside the if statement will execute and if the given condition is false, then the code present inside the else statement will execute.

Or we can say that an if-else statement is the modified version of an if statement where an if statement can be followed by an optional else statement, which executes when the Boolean expression is false.

For example, Ram is going to market and his mother tells him that if you find apples on sale then buy them otherwise buy grapes. So here the if condition is “Apple on sale” and the else condition is “buy Grapes”. Hence Ram will buy Apple only when the if condition is true. Otherwise, he will buy grapes.

Syntax

Following is the syntax of the if…else statement −

if boolean_expression{ 
   /* statement(s) will execute if the boolean expression is true */
}
else{ /* statement(s) will execute if the    boolean expression is false */
}

If the Boolean expression evaluates to true, then the if block of code will be executed, otherwise else block of code will be executed.

Flow Diagram

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

Example

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

import Foundation

var varA:Int = 100;

/* Check the boolean condition using if statement */
if varA < 20 {
   /* If the condition is true then print the following */
   print("varA is less than 20");

} else {
   /* If the condition is false then print the following */
   print("varA is not less than 20");
}

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

Output

It will produce the following output −

varA is not less than 20
Value of variable varA is 100

Example

Swift program to check even or odd numbers using if-else statement.

import Foundation

let num = 41

if num % 2 == 0 {
   print("Entered number is even.")
} else {
   print("Entered number is odd.")
}

Output

It will produce the following output −

Entered number is odd.

Example

Swift program to check the correct username using an if-else statement.

import Foundation

let username = "123Admin22"
let inputUsername = "123Admin22"

if username == inputUsername {
   print("Login successful.")
} else {
   print("Invalid username.")
}

Output

It will produce the following output −

Login successful.