Android Development with Kotlin

Elvis operator

The elvis operator is represented by a question mark followed by a colon (?:) and has a syntax such as the following:

    first operand ?: second operand 

The elvis operator works as follows: if first operand is not null, then this operand will be returned, otherwise second operand will be returned. The elvis operator allows us to write very concise code.

We can apply the elvis operator to our example to retrieve the variable locked, which will always be non-nullable:

override fun onCreate(savedInstanceState: Bundle?) { 
super.onCreate(savedInstanceState) 
val locked: Boolean = savedInstanceState?.getBoolean("locked") ?: false 
} 

In the preceding example, the elvis operator will return a value of the savedInstanceState?.getBoolean("locked") ...