Understanding a parameter that is initialized as an extension function

Question

In the following code the parameter type for modelInitializer is CalendarMonthTitleModelBuilder.()

What does the .() mean?. I believe the dot r

Answer 1

First of all ()->Unit is a lambda. And this lambda has a this, and it's type is the CalendarMonthTitleModelBuilder. It's called lambda with a receiver.

So inside modelInitializer you can access to CalendarMonthTitleModelBuilder as you are inside this class: using this.

For example, I assume that CalendarMonthTitleModelBuilder has a someMethod:

val epoxyController: EpoxyController = EpoxyController()

epoxyController.calendarMonthTitle {
    // inside these curlies `this: CalendarMonthTitleModelBuilder = CalendarMonthTitleModel_()`
    this.someMethod() //you can use 'this' inside this lambda
    someMethod() // or as usual just skip writing 'this', just access `CalendarMonthTitleModelBuilder` methods as you inside it's class

}

This feature is essential in building DSLs.

Here is a link to documentation.