Optional

An implementation of Optional for Kotlin.

Optional is a container that may or may not contain a single non-nullable value. It can be used instead of null references when null values are prohibited, like in RxJava 2.

Download

Gradle:

repositories {
  jcenter()
}

dependencies {
  compile 'io.michaelrocks:optional:1.0.1'
}

Usage

You can create an Optional in several ways.

1. By accessing Optional subclasses directly.

val optional1 = Optional.Some("Value")
val optional2 = Optional.None

2. By calling convenience functions.

val optional1 = some("Value")
val optional2 = none()

3. By invoking toOptional() extension function on some value.

val optional1 = "Value".toOptional()
val optional2 = null.toOptional()

To get a value back from an Optional you can invoke one of get() functions on the Optional reference.

val optional1 = some("Value")
val optional2 = none()

optional1.get() // returns "Value"
optional2.get() // throws NoSuchElementException

optional1.getOrNull() // returns "Value"
optional2.getOrNull() // returns null

optional1.getOrElse { "Other value" } // returns "Value"
optional2.getOrElse { "Other value" } // returns "Other value"

There're a number of functions to work with an Optional as with a Collection, such as filter, map, flatMap and many others. Moreover, you can convert an Optional to a Collection, an Iterable, or a Sequence.

License

Copyright 2016 Michael Rozumyanskiy

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.