Let function is another way to solve null problem in kotlin.
When you have such problem:
var favoriteColor: String? = null
...
...
return if f(avoriteColor !== null) getLastLetter(favoriteColor) else ""
The problem is ‘favoriteColor‘ might change, so smart casting is complaining about this.
The way to solve the problem is using let function.
val hello = "Hello World" val uppercaseHello = hello.toUpperCase() var uppercaseHello = hello.let {x -> x.toUpperCase()} var uppercaseHello = hello.let {it.toUpperCase()}
Solution:
var favoriteColor: String? = null fun getLastLetter(a: String) = a.takeLast(1) fun getLastLetterOfColor(): String { favoriteColor?.let {getLastLetter(it)} ?: "" }
原文：https://www.cnblogs.com/Answer1215/p/13893387.html