Kotlin has introduced a new feature called if as an expression, which makes a programmer's life much easier. Instead of assigning a value in each if statement, Kotlin returns the value from a successful code block, which can be stored in a variable. Before writing an if statement, add a variable name with an assignment operator as follows:

grade = if (studentMarks >= 90) {
    "A"
}

See the following example with if as an expression, where grade will be assigned depending on studentMarks:

fun main(args: Array<String>) {
 val studentMarks = 95
 var grade = if (studentMarks >= 90) {
 "A"
 } else if (studentMarks >= 80) {
 "B"
 } else if (studentMarks >= 70) {
 "C"
 } else if (studentMarks >= 60) {
 "D"
 } else {
 "F"
 }
 println ( "Student achieved " + grade )
}

Notice that it is not required to write grade = "A" or grade = "D" in each else…if block, but while using if as an expression, there is one thing to remember—if as an expression cannot be used without an else statement:

val grade = if (studentMarks >= 90) {
    "A"
}

Kotlin will throw the following compile-time error:

'if' must have both main and 'else' branches if used as an expression