Invoking Action by reference in Kotlin - kotlin

Question

I've a Map of (key, value) where the value is a predefined function.
I want to iterate the input param in the Mp and check where the key is matching with the input parameter, then invoke the equivalent function, something like this
My code required to be something like below:
fun fn1: Unit { // using Unit is optional
println("Hi there!")
}
fun fn2 {
println("Hi again!")
}
fun MainFun(x: int){
val map: HashMap<Int, String> = hashMapOf(1 to fn1, 2 to fn2)
for ((key, value) in map) {
// if key = x then run/invoke the function mapped with x, for example if x = 1 then invoke fn1
}
}
Notes: I read something like below, but could not know how to us them:
inline fun <K, V> Map<out K, V>.filter(
predicate: (Entry<K, V>) -> Boolean
): Map<K, V> (source)
val russianNames = arrayOf("Maksim", "Artem", "Sophia", "Maria", "Maksim")
val selectedName = russianNames
.filter { it.startsWith("m", ignoreCase = true) }
.sortedBy { it.length }
.firstOrNull()

Answer 1

Hi I hope this would help you.
fun fn1() {
println("Hi there!")
}
fun fn2() {
println("Hi again!")
}
fun main(args: IntArray){
val map = hashMapOf(
1 to ::fn1,
2 to ::fn2)
map.filterKeys { it == args[0] } // filters the map by comparing the first int arg passed and the key
.map { it.value.invoke() } // invoke the function that passed the filter.
}
If the keyis RegEx then map.filterKeys { Regex(it).matches(x) } can be used, below full example of it Try Kotlin:
data class Person(val name: String,
val age: Int? = null)
val persons = listOf(Person("Alice"),
Person("Bob", age = 23))
fun old() {
val oldest = persons.maxBy { it.age ?: 0 }
println("The oldest is: $oldest")
}
fun young() {
val youngest = persons.minBy { it.age ?: 0 }
println("The youngest is: $youngest")
}
fun selection(x: String) {
val map = mapOf(
"old|big" to ::old,
"new|young" to ::young)
map.filterKeys { Regex(it).matches(x) }
.map { it.value.invoke() }
}
fun main(args: Array<String>) {
selection("new")
}

Answer 2

fun fn1() {
println("Hi there!")
}
fun fn2() {
println("Hi again!")
}
fun main(args: Array<Int>){
val map = hashMapOf(1 to ::fn1, 2 to ::fn2)
map.forEach { key, function -> function.invoke() }
}
This will do the work but your code does not even have the correct syntax. You should learn the basic first.