CODEWITHSUNDEEP
kotlin
ceving
ceving

Reputation: 23794

What consequences does it have, if I use `Any` as a type parameter constraint in general?

I can use an unconstrained type paramter:

interface State<V>

or I can use a constrained type parameter:

interface State<V: Any>

This seems to be the same, because "In Kotlin, everything is an object [...]". But this may be deceptive. What consequences does it have, if I favor the second instead of the first?

Upvotes: 1

Views: 52

Answers (1)

broot
broot

Reputation: 28302

Please be aware the default upper bound is not Any, but Any?. There is no difference if we write interface State<V> or interface State<V : Any?> - this is the same thing.

However, interface State<V : Any> is different, it constrains T to be not nullable type:

interface State<V : Any>

class StringState : State<String> // ok
class NullableStringState : State<String?> // compile error

Both above classes compile fine if we don't specify the upper bound or we set it to Any?.

Upvotes: 1

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