Kotlin Ternary Operator

Ternary operator in Kotlin

When it comes to expressing conditional logic in programming, many languages offer a succinct and elegant solution known as the ternary operator. However, Kotlin takes a slightly different approach. Unlike some other languages, ternary operator in Kotlin is not provided as a built-in feature. However, Kotlin offers graceful substitutes that deliver comparable functionality.

However, this apparent omission of the ternary operator in Kotlin doesn't hinder its capability to elegantly handle conditional expressions. Instead of relying on a standalone ternary operator, Kotlin offers a variety of constructs that together accomplish the same tasks.

if and when Expressions

Unlike other programming languages, both if and when are expressions in Kotlin. What this means is that the outcome of these expressions can be assigned to a variable.

Leveraging this characteristic, both if and when can serve as alternatives to the ternary operator in Kotlin, each in its unique manner.

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Using if-else

Let us explore utilizing the if expression as a substitute for the ternary operator in Kotlin.

Consider the following code snippet.

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In this example, if the value of a is true, the result variable is assigned the boolean value true. Otherwise, it receives the boolean value false.

It is important to recognize that the resultant data type depends on the expression found on the right side. Generally, the type defaults to Any. For instance, if the right-side expression holds a String type, the outcome will also be of String type. Consider the following code snippet.

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Using when

Utilizing the when expression, we can construct a pseudo-ternary operator in Kotlin as well. Here is how we go about doing it.

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This code snippet above is simple, readable and direct. When the condition (num%2 == 0) evaluates to true, the result is set to "Even". Conversely, when the condition is false, the result becomes "Odd". The behaviour is similar to what the ternary operator offers in other programming languages.

Elvis Operator

We often use if expressions to retrieve a non-null value or provide a default one in case of null. Consider the following example.

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This behavior can also be achieved using when expressions. Consider the following code snippet.

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Given the frequency of its usage, Kotlin offers a dedicated operator for this scenario.

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This operator, known as the Elvis operator (?:), exhibits a simple yet powerful functionality. It returns the operand if it's non-null; otherwise, it returns the default value present on the right side of the operator.

DSL

Certainly, there's a strong urge to build something similar to a ternary operator using Kotlin's DSL (Domain-Specific Language). But due to Kotlin's strict rules, it's not possible to perfectly recreate the exact way traditional ternary operators work.