Scala: Options Cheat Sheet - A quick cheatsheet for beginners, with examples

Option	Description
`Some(42)`	Construct a non empty optional value.
`None`	The singleton empty optional value.
`Option(null) == None Option(obj.unsafeMethod)` but `Some(null) != None`	Null-safe optional value factory.
`val optStr: Option[String] = None` same as `val optStr = Option.empty[String]`	Explicit type for empty optional value. Factory for empty optional value.
`val name: Option[String] =` `request.getParameter("name")` `val upper = name.map {` `_.trim` `} filter {` `_.length != 0` `} map {` `_.toUpperCase } println(upper.getOrElse(""))`	Pipeline style.
`val upper = for {` `name <- request.getParameter("name")` `trimmed <- Some(name.trim)` `if trimmed.length != 0` `upper <- Some(trimmed.toUpperCase)` `} yield upper println(upper.getOrElse(""))`	For-comprehension syntax.
`option.map(f(_))` same as `option match {` `case Some(x) => Some(f(x))` `case None => None` `}`	Apply a function on the optional value.
`option.flatMap(f(_))` same as `option match {` `case Some(x) => f(x)` `case None => None` `}`	Same as map but function must return an optional value.
`optionOfOption.flatten` same as `optionOfOption match {` `case Some(Some(x)) => Some(x)` `case _ => None` `}`	Extract nested option.
`option.foreach(f(_))` same as `option match {` `case Some(x) => f(x)` `case None => ()` `}`	Apply a procedure on optional value.
`option.fold(y)(f(_))` same as`option match {` `case Some(x) => f(x)` `case None => y` `}`	Apply function on optional value, return default if empty.
`option.collect {` `case x => ...` `}` same as `option match {` `case Some(x) if f.isDefinedAt(x) => ...` `case Some(_) => None case None => None` `}`	Apply partial pattern match on optional value.
`option.isDefined` same as`option match {` `case Some(_) => true` `case None => false` `}`	`true` if not empty.
`option.isEmpty` same as `option match {` `case Some(_) => false` `case None => true` `}`	`true` if empty.
`option.nonEmpty` same as`option match {` `case Some(_) => true` `case None => false` `}`	`true` if not empty.
`option.size` same as `option match {` `case Some(_) => 1` `case None => 0` `}`	`0` if empty, otherwise `1`.
`option.orElse(Some(y))` same as `option match {` `case Some(x) => Some(x)` `case None => Some(y)` `}`	Evaluate and return alternate optional value if empty.
`option.getOrElse(y)` same as `option match {` `case Some(x) => x` `case None => y` `}`	Evaluate and return default value if empty.
`option.get` same as `option match {` `case Some(x) => x` `case None => throw new Exception` `}`	Return value, throw exception if empty.
`option.orNull` same as `option match {` `case Some(x) => x` `case None => null` `}`	Return value, `null` if empty.
`option.filter(f)` same as `option match {` `case Some(x) if f(x) => Some(x)` `case _ => None` `}`	Optional value satisfies predicate.
`option.filterNot(f(_))` same as `option match {` `case Some(x) if !f(x) => Some(x)` `case _ => None` `}`	Optional value doesn’t satisfy predicate.
`option.exists(f(_))` same as `option match {` `case Some(x) if f(x) => true` `case Some(_) => false` `case None => false` `}`	Apply predicate on optional value or `false` if empty.
`option.forall(f(_))` same as `option match {` `case Some(x) if f(x) => true` `case Some(_) => false` `case None => true` `}`	Apply predicate on optional value or `true` if empty.
`option.contains(y)` same as `option match {` `case Some(x) => x == y` `case None => false` `}`	Checks if value equals optional value or `false` if empty.

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