HLists

Basic support for heterogeneous lists, aka HLists.

An HList can be constructed like so:

import net.liftweb.common.HLists._

trait Base
case class Type1(value: String) extends Base
case class Type2(otherValue: String) extends Base

val myHList = Type1("Value") :+: Type2("Other Value") :+: HNil
myHList match {
  case firstThing :+: secondThing :+: HNil =>
    println(firstThing.value)
    println(secondThing.otherValue)
}

Above, we see that the HList preserved the value of the types of its members, otherwise we wouldn't have been able to fetch value and otherValue, respectively.

Trying the same thing with a list won't work:

val myList = Type1("Value") :: Type2("Other Value") :: Nil
myList match {
  case firstThing :: secondThing :: Nil =>
    // error: value value is not a member of Product with Serializable with Base
    println(firstThing.value)
}

This is because value is not defined in Base. The inferred type of the List has to be a common ancestor class or trait of Type1 and Type2, and no such type has a value method.

Linear Supertypes

AnyRef, Any

Type Members

final case class :+:[+H, +T <: HList](head: H, tail: T) extends HList with Product with Serializable

The HList cons cell, which represents one part of an HList in linked list style.
The HList cons cell, which represents one part of an HList in linked list style.
Carries the information about the type of this element, plus the HList type of the rest of the list.
You can use :+: to make this HList longer:
```
scala> val first = Type1("Value") :+: HNil
first: net.liftweb.common.HLists.HCons[Type1,net.liftweb.common.HLists.HNil] = Type1(Value) :+: HNil
scala> Type2("Other Value") :+: first
res0: net.liftweb.common.HLists.HCons[Type2,
        net.liftweb.common.HLists.HCons[Type1,
          net.liftweb.common.HLists.HNil]] =
      Type2(Other Value) :+: Type1(Value) :+: HNil
```
sealed trait HList extends AnyRef

The base trait for HLists.
The base trait for HLists. Functions that take HLists will need a type parameter subtype of HList:
```
def myHListFunction[T <: HList](list: HList) = {
  println(s"This HList has ${list.length} items!")
}
```
implicit final class HListMethods[ListSoFar <: HList] extends AnyRef

Provides the methods that can be used on an HList.
Provides the methods that can be used on an HList. These are set apart here due to certain issues we can experience otherwise with the type variance on the :+: class.
final class HNil extends HList

The last element of an HList.
The last element of an HList. This is the starting point for an HList, and you can use :+: to start one based on it:
```
scala> Type1("Value") :+: HNil
res0: net.liftweb.common.HLists.HCons[Type1,net.liftweb.common.HLists.HNil] = Type1(Value) :+: HNil
```

Value Members

final def !=(arg0: Any): Boolean

Definition Classes
AnyRef → Any
final def ##(): Int

Definition Classes
AnyRef → Any
final def ==(arg0: Any): Boolean

Definition Classes
AnyRef → Any
val HNil: HNil

The HNil singleton.
final def asInstanceOf[T0]: T0

Definition Classes
Any
def clone(): AnyRef

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( ... )
final def eq(arg0: AnyRef): Boolean

Definition Classes
AnyRef
def equals(arg0: Any): Boolean

Definition Classes
AnyRef → Any
def finalize(): Unit

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( classOf[java.lang.Throwable] )
final def getClass(): Class[_]

Definition Classes
AnyRef → Any
def hashCode(): Int

Definition Classes
AnyRef → Any
final def isInstanceOf[T0]: Boolean

Definition Classes
Any
final def ne(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def notify(): Unit

Definition Classes
AnyRef
final def notifyAll(): Unit

Definition Classes
AnyRef
final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
def toString(): String

Definition Classes
AnyRef → Any
final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )

Related Doc: package common

object HLists

Type Members

final case class :+:[+H, +T <: HList](head: H, tail: T) extends HList with Product with Serializable

sealed trait HList extends AnyRef

implicit final class HListMethods[ListSoFar <: HList] extends AnyRef

final class HNil extends HList

Value Members

final def !=(arg0: Any): Boolean

final def ##(): Int

final def ==(arg0: Any): Boolean

val HNil: HNil

final def asInstanceOf[T0]: T0

def clone(): AnyRef

final def eq(arg0: AnyRef): Boolean

def equals(arg0: Any): Boolean

def finalize(): Unit

final def getClass(): Class[_]

def hashCode(): Int

final def isInstanceOf[T0]: Boolean

final def ne(arg0: AnyRef): Boolean

final def notify(): Unit

final def notifyAll(): Unit

final def synchronized[T0](arg0: ⇒ T0): T0

def toString(): String

final def wait(): Unit

final def wait(arg0: Long, arg1: Int): Unit

final def wait(arg0: Long): Unit

Inherited from AnyRef

Inherited from Any

Ungrouped