The following example demonstrates its use cases. If a variable can be null, its not safe to call a method on the variable because this. This smart casting works for null checks, type checks, or any condition that satisfies a contract. When dealing with Maps in Kotlin, sometimes we’re only interested in entries for which the value is not null.Although the Kotlin Standard Library contains a filterValues function that seems to be appropriate, this function does not do any type conversions, resulting in a Map which won’t contain null values, but is still a Map with values of a nullable type according to the compiler. Kotlin tries to provide null-safety even when the variable could be changed from another thread. It is a way to indicate which variables can possibly hold a null value.
Thus let saves us from the if else null checker too Kotlin run Kotlin run is another interesting function. Kotlin is smart enough to recognize that the condition for executing the branch is that languageName does not hold a null value, so you do not have to treat languageName as nullable within that branch.
As a result, we cant give a variable a null value because it will trigger a compilation error.
Transforming example using run: val companyName = user?. The code inside the let expression is executed only when the property is not null. Kotlins variables are all non-nullable by default. You can use the Kotlin extension functions apply() or run() depending on whether you want it to be fluent ( returning this at end) or transforming ( returning a new value at end):
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