Kotlin Code Pills — Safe Calls

In Kotlin , one of the option is the safe call operator, written with ?.

var b: String? = null
println(b?.length)

Prints b.lenght if b is not null, otherwise prints null.

Safe calls are useful for chains like

person?.address?.city

If any field of the chain is null, returns null.

Another option, if you are sure that the nullable variable definitely won’t be null. Than you can use !! .

val city = person?.address?.city ?: "Istanbul"
var result = location[city]!!

I am 100% confident that result is a non-null entry.

See you next Code pills.