mikolak-net / scala-common

Tiny independent libraries with a single purpose, often a single class

scala-common

Tiny independent libraries with a single purpose, often a single class.

Tagging

Tag instances with arbitrary types. Useful if you'd like to differentiate between instances on the type level without runtime overhead. Tags are only used at compile-time to provide additional type safety.

An instance of type T tagged with type U has type T @@ U (which is sugar for @@[T, U]). You can only use x: T @@ U when an instance of type T @@ V is expected when U is a subtype of V (U <: V).

The tag can be any type, but usually it is just an empty marker trait.

To add tags to existing instances, you can use the taggedWith[_] method, which returns a tagged instance (T.taggedWith[U]: T @@ U). Tagged instances can be used as regular ones, without any constraints.

SBT dependency:

libraryDependencies += "com.softwaremill.common" %% "tagging" % "1.0.0"

Example:

import com.softwaremill.tagging._

class Berry()

trait Black
trait Blue

val berry = new Berry()
val blackBerry: Berry @@ Black = berry.taggedWith[Black]
val blueBerry: Berry @@ Blue = berry.taggedWith[Blue]

// compile error: val anotherBlackBerry: Berry @@ Black = blueBerry

Original idea by Miles Sabin. Similar implementations are also available in Shapeless and Scalaz.

Id generator

Generate unique ids. A default generator is provided, based on Twitter Snowflake, which generates time-based ids.

SBT depedency:

libraryDependencies += "com.softwaremill.common" %% "id-generator" % "1.0.0"

Future Try extensions

Provides two utility methods for extending Future:

• tried: Future[Try[T]] - reifying the Future's result.
• transformTry(f: Try[T] => Try[S]): Future[S] - corresponds to 2.12's new transform variant, allowing to supply a single function (if, for example, you already have one handy), instead of two. Note: unfortunately, it was not possible to name this method transform, due to how scalac handles implicit resolution.

SBT depedency:

libraryDependencies += "com.softwaremill.common" %% "futuretry" % "1.0.0"

Example:

val myFuture: Future[Foo] = ...
val myUsefulTransformer: Try[Foo] => Try[Bar] = ...

def someWeirdApiMethod(future: Future[Try[Foo]])
 
import com.softwaremill.futuretry._

someWeirdApiMethod(myFuture.tried)

val myBetterFuture: Future[Bar] = myFuture.transformTry(myUsefulTransformer)