If as an Expression

What Does "If as an Expression" Mean?

In Kotlin, the if statement is not just a control flow statement—it is also an expression. This means that if can return a value, just like a variable or a function call. You can assign the result of an if expression directly to a variable.

How Is This Different from Java?

In Java and many other languages, if is only a statement. You cannot assign the result of an if directly to a variable. You must use extra lines of code to set the value:

int max;
if (a > b) {
    max = a;
} else {
    max = b;
}

In Kotlin, you can do this in one step:

val max = if (a > b) a else b

Why Is This Useful?

• Makes code shorter and clearer;
• Reduces the risk of mistakes by keeping related logic together;
• Encourages you to think in terms of expressions, not just actions.

Using If as an Expression

You can use if anywhere a value is needed. For example, you can return the result of an if expression from a function, or use it as part of a larger calculation. Both the then and else branches must return a value.

val result = if (score >= 60) "Pass" else "Fail"

Multi-Line If Expressions

If you need more logic in each branch, you can use curly braces. The last expression in each branch is the value returned:

val message = if (user.isLoggedIn) {
    println("Welcome back!")
    "User logged in"
} else {
    println("Please log in.")
    "User not logged in"
}

Key Takeaways

• In Kotlin, if is an expression that produces a value;
• You can assign the result of an if expression to a variable;
• This feature leads to more concise and readable code.