Higher order functions

Definition

• Higher-order functions are the ones that take functions as parameters or return function as a result.
• We can even store the higher-order function in a variable and a data structure.
• They enable functional programming concepts and allow you to write more concise and expressive code.

Background

• kotlin literals
• Lamda Expression

Passing function as parameter

Define a caller in view

AppButton(text = "Passing Functions as parameter", onClick = {
            // Here will will calculate the square of a number
            val input = 5
            // Call the functionality
            val result = viewModel.performOperation(input) { input ->
                input * input
            }
            println(result)
})

Define the calling function in the view model

fun performOperation(input: Int, operation: (Int) -> Int): Int {
        return operation(input)
}

Returning Function

Define a caller in view

AppButton(text = "Passing Functions as parameter", onClick = {
            // We pass a operation here
            val addFunction = viewModel.createCalculator("add")
            // We use the operation passed above to pass values for it
            val resultAdd = addFunction(5, 3) // Result is 8
            println("Result (Add): $resultAdd")
})

Define the calling function in the view model

fun createCalculator(operator: String): (Int, Int) -> Int {
        return when (operator) {
            "add" -> { a, b -> a + b }
            "subtract" -> { a, b -> a - b }
            "multiply" -> { a, b -> a * b }
            "divide" -> { a, b -> if (b != 0) a / b else 0 }
            else -> throw IllegalArgumentException("Unknown operator: $operator")
        }
}