February 2018
Intermediate to advanced
350 pages
7h 35m
English
Content preview from Functional Kotlin
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The Nothing type
Nothing is the type that sits at the bottom of the entire Kotlin hierarchy. Nothing extends all Kotlin types, including Nothing?.
But, why do we need a Nothing and Nothing? types?
Nothing represents an expression that can't be executed (basically throwing exceptions):
val result: String = nullableCupcake?.eat() ?: throw RuntimeException() // equivalent to nullableCupcake!!.eat()
On one hand of the Elvis operator, we have a String. On the other hand, we have Nothing. Because the common type between String and Nothing is String (instead of Any), the value result is a String.
Nothing also has a special meaning for the compiler. Once a Nothing type is returned on an expression, the lines after that are marked as unreachable. ...
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