How to Return Value from Function in Kotlin: Simple Guide

In Kotlin, you return a value from a function using the return keyword followed by the value. The function must declare the return type after the function name using a colon, like fun example(): Int.

Syntax

To return a value from a function in Kotlin, you declare the return type after the function name using a colon. Inside the function body, use the return keyword followed by the value you want to send back.

• fun: keyword to declare a function
• functionName: name of the function
• (): ReturnType: parentheses for parameters and colon with return type
• return value: sends the value back to the caller

kotlin

fun functionName(): ReturnType {
    return value
}

Example

This example shows a function that returns the sum of two numbers. It declares the return type Int and uses return to send the result back.

kotlin

fun add(a: Int, b: Int): Int {
    return a + b
}

fun main() {
    val result = add(5, 3)
    println("Sum is: $result")
}

Output

Sum is: 8

Common Pitfalls

One common mistake is forgetting to specify the return type when the function returns a value. Another is missing the return keyword inside the function body. Also, if the function has a single expression, you can use the expression body syntax without return.

kotlin

/* Wrong: Missing return type */
fun multiply(a: Int, b: Int) {
    return a * b // Error: function must declare return type
}

/* Correct: Specify return type */
fun multiply(a: Int, b: Int): Int {
    return a * b
}

/* Shorter syntax for single expression */
fun multiplyShort(a: Int, b: Int): Int = a * b

Quick Reference

Remember these tips when returning values in Kotlin functions:

• Always declare the return type if your function returns a value.
• Use return keyword to send the value back.
• For single-expression functions, use the concise syntax without braces.
• Functions without return type or with Unit return nothing.

Key Takeaways

Use the return keyword followed by the value to return from a Kotlin function.

Declare the return type after the function name with a colon.

Single-expression functions can omit braces and the return keyword.

Functions without a return type or with Unit return no meaningful value.

Always match the declared return type with the returned value type.