CODEWITHSUNDEEP
kotlin
Michal Vician
Michal Vician

Reputation: 2545

Undetected throw declaration (Kotlin)

Let's have a function which just computes something in try-catch and returns the result:

    private fun compute(): String {
        
        return try {
            // do some computation
            // ...
            "result"
            
        } catch(t: Throwable) {
            throw RuntimeException("Uups") // <-- GOAL: extract this to a dedicated method
        }
    }

I would like to extract the throw declaration to a separate function (which contains the my boilerplate code).

However, I'm unable to compile such setup in Kotlin.

A simplistic (and still uncompilable) version of the described problem:

    private fun compute(): String {

        return try {
            // do some computation
            // ...
            "result"

        } catch(t: Throwable) {
            justThrow() // <-- NOT COMPILABLE, STRING EXPECTED
        }
    }

    @Throws(RuntimeException::class)
    private fun justThrow() {
        // some boilerplate code
        // ...
        throw RuntimeException("Uups")
    }

How write justThrow() method in Kotlin so that the whole code is compilable?

In Java this case would be detected by a compiler (I suppose).

Kotlin version: 1.4.21

Upvotes: 0

Views: 58

Answers (1)

Adrian K
Adrian K

Reputation: 4833

You can declare the return type of your method as Nothing. This type can be used for any method that does not return normally. That might be because it will always throw an exception, or simply never returns at all, for instance because it contains an infinite loop.

private fun justThrow(): Nothing {
    // some boilerplate code
    // ...
    throw RuntimeException("Uups")
}

Upvotes: 4

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