13-lambdas-with-receiver.kt

package org.athenian

// See: https://proandroiddev.com/writing-dsls-in-kotlin-part-1-7f5d2193f277

fun main() {

  data class Address(var street: String? = null, var city: String? = null)

  data class Person(var name: String? = null, var age: Int? = null, var address: Address? = null)

  fun lambdaArg(): Person {

    // Lambda arg
    fun person(block: (Person) -> Unit): Person {
      val p = Person()
      block(p)
      //block.invoke(p)
      return p
    }

    return person { p: Person ->
      p.name = "John"
      p.age = 25
    }
  }

  fun lambdaWithReceiverArg(): Person {

    // Lambda with receiver arg
    fun person(block: Person.() -> Unit): Person {
      val p = Person()
      p.block()
      //p.apply(block)
      return p
    }

    return person {
      this.name = "Mary"
      this.age = 26
    }
  }

  fun embeddedLambdaWithReceiverArg(): Person {

    fun person(block: Person.() -> Unit): Person = Person().apply(block)

    fun Person.address(block: Address.() -> Unit) {
      address = Address().apply(block)
    }

    return person {
      name = "Tracey"
      age = 21
      address {
        street = "123 Main"
        city = "Houston"
      }
    }
  }

  println("Lambda Arg: ${lambdaArg()}")
  println("Lambda With Receiver Arg: ${lambdaWithReceiverArg()}")
  println("Embedded Lambda With Receiver Arg: ${embeddedLambdaWithReceiverArg()}")
}