Mastering Kotlin

Making it easy to use

Currently, we have no @DslMarker annotation in place so, as we start to nest these function calls, we have access to functions for multiple different receivers. For example, in the following code snippet, we can call the soda function within the init block for Pizza:

+HawaiianPizza {    +Pepperoni    soda(Coke) // want to avoid this}

This behavior is not ideal because it doesn't make sense to add a Soda to Pizza. So, by default, we want to limit this behavior. To do that, we can create a new @DslMarker annotation:

@DslMarkerannotation class ItemTagMarker

We can then add that to the base class for our Items:

@ItemTagMarkerabstract class Item(val name: String)

With that annotation in place, the compiler will mark it as an error ...