misc
A typeclass which witnesses that type A can be wrapped into trait or abstract class B
Like Opt but does have a counterpart for Some(null).
Base trait for enums implemented as sealed hierarchy with case objects where every enum value has distinct textual representation (name).
Base trait for enums implemented as sealed hierarchy with case objects where every enum value has distinct textual representation (name).
Typically, if a trait or class extends NamedEnum, its companion object extends NamedEnumCompanion.
Enum values can then be looked up by name using NamedEnumCompanion.byName.
Base trait for companion objects of sealed traits that serve as named enums.
Base trait for companion objects of sealed traits that serve as named enums. NamedEnumCompanion is an
extension of SealedEnumCompanion which additionally requires that every enum value has distinct string
representation. Values can then be looked up by that representation using NamedEnumCompanion.byName
Example:
sealed abstract class Color(val name: String) extends NamedEnum object Color extends NamedEnumCompanion[Color] { case object Red extends Color("red") case object Blue extends Color("blue") case object Green extends Color("green") // it's important to explicitly specify the type so that `caseObjects` macro works properly val values: List[Color] = caseObjects }
NamedEnumCompanion also automatically provides implicit typeclass instances for
GenKeyCodec and GenCodec.
Like Option but implemented as value class (avoids boxing) and treats null as no value.
Like Option but implemented as value class (avoids boxing) and treats null as no value.
Therefore, there is no equivalent for Some(null).
If you need a value-class version of Option which differentiates between no value and null value,
use NOpt.
OptArg is like Opt except it's intended to be used to type-safely express optional method/constructor
parameters while at the same time avoiding having to explicitly wrap arguments when passing them
(thanks to the implicit conversion from A to OptArg[A]).
OptArg is like Opt except it's intended to be used to type-safely express optional method/constructor
parameters while at the same time avoiding having to explicitly wrap arguments when passing them
(thanks to the implicit conversion from A to OptArg[A]). For example:
def takesMaybeString(str: OptArg[String] = OptArg.Empty) = ??? takesMaybeString() // default empty value is used takesMaybeString("string") // no explicit wrapping into OptArg required
Note that like Opt, OptArg assumes its underlying value to be non-null and null is translated into OptArg.Empty.
It is strongly recommended that OptArg type is used ONLY in signatures where implicit conversion A => OptArg[A]
is intended to work. You should not use OptArg as a general-purpose "optional value" type - other types like
Opt, NOpt and Option serve that purpose. For this reason OptArg deliberately does not have any "transforming"
methods like map, flatMap, orElse, etc. Instead it's recommended that OptArg is converted to Opt,
NOpt or Option as soon as possible (using toOpt, toNOpt and toOption methods).
Like Opt but has better Java interop thanks to the fact that wrapped value has type A instead of Any.
Like Opt but has better Java interop thanks to the fact that wrapped value has type A instead of Any.
For example, Scala method defined like this:
def takeMaybeString(str: OptRef[String]): Unit
will be seen by Java as:
public void takeMaybeString(String str);and null will be used to represent absence of value.
This comes at the cost of A having to be a nullable type. Also, empty value is represented internally using null
which unfortunately makes OptRef suffer from SI-7396 (hashCode fails on OptRef.Empty which means that you
can't add OptRef values into hash sets or use them as hash map keys).
Trait to be extended by enums whose values are ordered by declaration order.
Trait to be extended by enums whose values are ordered by declaration order. Ordering is derived from SourceInfo object, which is typically accepted as an implicit, e.g.
sealed abstract class MyOrderedEnum(implicit val sourceInfo: SourceInfo) extends OrderedEnum object MyOrderedEnum { case object First extends MyOrderedEnum case object Second extends MyOrderedEnum case object Third extends MyOrderedEnum val values: List[MyOrderedEnum] = caseObjects }
In the example above, values is guaranteed to return First, Second and Third objects in exactly that order.
Base trait for companion objects of sealed traits that serve as enums, i.e.
Base trait for companion objects of sealed traits that serve as enums, i.e. their only values are case objects. For example:
sealed trait SomeEnum object SomeEnum extends SealedEnumCompanion[SomeEnum] { case object FirstValue extends SomeEnum case object SecondValue extends SomeEnum case object ThirdValue extends SomeEnum // it's important to explicitly specify the type so that `caseObjects` macro works properly val values: List[SomeEnum] = caseObjects }
Macro-materialized implicit value that provides information about callsite source file position.
Macro-materialized implicit value that provides information about callsite source file position.
It can be used in runtime for logging and debugging purposes.
Similar to Scalactic's Position, but contains more information.
Base class for sealed enums which can be used as key type for a TypedMap.
Creates reversed partial function.
Like Opt but does have a counterpart for
Some(null). In other words, NOpt is a "nullable Opt".