Higher Order Function Kotlin

Definition:

A function which can accepts a function as parameter or can returns a function is called Higher-Order function. Instead of Integer, String or Array as a parameter to function, we will pass anonymous function or lambdas.

What is () -> unit in Kotlin?

The Unit type in Kotlin is the equivalent to the void type in Java.

Example:

typealias HigherFun = (String,String) -> Unit
typealias Lmbd=  () -> Unit

var lambda = { println("Tell me about yourself....?") }

fun callingHigherFuncLmbd( lmbd: Lmbd ) {
    lmbd()                //Invoke Lambda Expression  
    //or by invoke method 
    //lmbd.invoke()
}

fun callingHigherFunWithParam(listener: HigherFun){
    listener("Good Evening ","Jack") //Invoke higher oreder Fun
    //or by invoke method 
    // listener.invoke("","")
}

fun callingHigherFunWithParams(name :String,listener: HigherFun){
    listener("I'm ",name+" with basic programming skills.") //Invoke higher oreder Fun
    //or by invoke method 
    // listener.invoke("","")
}


fun main(args: Array<String>) {

    val name ="Jones"

    callingHigherFuncLmbd(lambda) // sepertate fun for calling lmbd higher order functiom

    callingHigherFunWithParam { var1: String, var2: String ->
        println(var1+var2) // Definition of Higher Order Fun with param
    }

    // sepertate fun for calling  higher order functiom with param

    callingHigherFunWithParams(name,{ var1: String, var2: String ->
        println(var1+var2)
    })
}