The let function

Another tool to deal with nullable variables is the let function. This is actually not an operator, nor a language special construct. It is a function defined in the Kotlin standard library. Let's see the syntax of let combined with the safe call operator:

    override fun onCreate(savedInstanceState: Bundle?) { 
        super.onCreate(savedInstanceState) 
 
        savedInstanceState?.let { 
            println(it.getBoolean("isLocked")) // 1 
        } 
    } 

1. savedInstanceState inside the let function can be accessed using the it variable.

As mentioned before, the right-hand expression of the safe call operator will be only evaluated if the left-hand side is not null. In this case, the right-hand side is a let function that takes another function (lambda) as a parameter. Code defined in the block after let will be executed if savedInstanceState is not null. We will learn more about it and how to define such functions in Chapter 7, Extension Functions and Properties.