2017-09-15 · It's important to note that while many of these look like functions in kotlin.collections, these are all provided by Kategory's Try. Providing defaults with getOrElse. This is used for retreiving the value for the Success subclass.

@kotlin.internal.InlineOnly public inline fun Map.getOrElse(key: K, defaultValue: -> V): V = get(key) ?: defaultValue() Which seems trivial at first glance, but is incorrect if V is nullable, which is allowed in Map. So if you use getOrElse on your map that can have null values, you're very likely making a mistake.

Returns a character at the given index or the result of calling the defaultValue function if the index is out of bounds of this char sequence. getOrElse. Returns the encapsulated value if this instance represents success or the result of onFailure function for the encapsulated Throwable exception if it is failure. Note, that this function rethrows any Throwable exception thrown by onFailure function. myInt = dat.getOrElse(index = 100, defaultValue = { i -> // use i to calcuate your Byte that should be returned // or return a fixed value i * 1 // for example}) Signature of getOrElse: fun ByteArray.getOrElse( index: Int, defaultValue: (Int) -> Byte): Byte. Share.

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These are equivalent to the ?: operator except this provides a better syntax when chaining methods. The lambda parameter version allows for lazy evaluation of the result e.g. It can contain two types: The Some wrapper around the value or None when it has no value.. We have a few different ways to create an Option:. val factory = Option.just(42) val constructor = Option(42) val emptyOptional = Option.empty() val fromNullable = Option.fromNullable(null) Assert.assertEquals(42, factory.getOrElse { -1 }) Assert.assertEquals(factory, constructor) Assert Kotlin comes with a wide range of extension methods to make collections manipulation easy. You can map, filter, find or whatever you want to do.

As we know there are two types of collections in Kotlin. Immutable collections. List: listOf; Map:mapOf; Set: setOf; And mutable collections. List: ArrayList, arrayListOf, mutableListOf; Map:HashMap, hashMapOf, mutableMapOf; Set: mutableSetOf, hashSetOf; Let’s practically learn about Kotlin mapOf. Kotlin mapOf Examples

Same for getOrPut() when overriding methods from Java where Kotlin isn't sure about the nullability of the Java code, you can always drop the ? nullability from your override if you are sure what the signature and functionality should be. @kotlin.internal.InlineOnly public inline fun Map.getOrElse(key: K, defaultValue: -> V): V = get(key) ?: defaultValue() Which seems trivial at first glance, but is incorrect if V is nullable, which is allowed in Map. So if you use getOrElse on your map that can have null values, you're very likely making a mistake.

Feb 18, 2018 Kotlin implemented its approach to null-safety that can leverage extra compiler support. Simply put, each type is non-nullable by default but can

If we had cheap, custom value types on the JVM, that would be a good solution. But alas, we do not. This is very much the case of Kotlin inheriting some JVM and Java stdlib baggage.

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Some and None are declared as top level types. No need to write Optional.Some or Optional.None.

myInt = dat.getOrElse(index = 100, defaultValue = { i -> // use i to calcuate your Byte that should be returned // or return a fixed value i * 1 // for example}) Signature of getOrElse: fun ByteArray.getOrElse( index: Int, defaultValue: (Int) -> Byte): Byte. Share.
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List is an ordered collection and can contain duplicate elements. You can access any element from its index. The List is more like an array with dynamic length, List is one of the most used Collection type.

This function is a shorthand for fold (onSuccess = { it }, onFailure = onFailure) (see fold ). val list = listOf(0, 10, 20) println(list.getOrElse(1) { 42 }) // 1. println(list.getOrElse(10) { 42 }) // 2.

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2021-02-09 · Fortunately, Kotlin has a handy, exception-safe method: fun parseInput(s : String) : Option = Option.fromNullable(s.toIntOrNull()) We wrap the parse result into an Option. Then, we’ll transform this initial value with some custom logic: fun isEven(x : Int) : Boolean // fun biggestDivisor(x: Int) : Int //

getOrElse() getOrElse() function returns the value for the given key, or the result of the defaultValue function if there was no entry for the given key.