Trait/Object

org.scalatest.enablers

Length

Related Docs: object Length | package enablers

Permalink

trait Length[T] extends AnyRef

Supertrait for Length typeclasses.

Trait Length is a typeclass trait for objects that can be queried for length. Objects of type T for which an implicit Length[T] is available can be used with the should have length syntax. In other words, this trait enables you to use the length checking syntax with arbitrary objects. As an example, the following Bridge class:

scala> import org.scalatest._
import org.scalatest._

scala> import enablers.Length
import enablers.Length

scala> import Matchers._
import Matchers._

scala> case class Bridge(span: Int)
defined class Bridge

Out of the box you can't use the should have length syntax with Bridge, because ScalaTest doesn't know that a bridge's span means its length:

scala> val bridge = new Bridge(2000)
bridge: Bridge = Bridge(2000)

scala> bridge should have length 2000
<console>:34: error: could not find implicit value for
    parameter len: org.scalatest.enablers.Length[Bridge]
      bridge should have length 2000
                         ^

You can teach this to ScalaTest, however, by defining an implicit Length[Bridge].

scala> implicit val lengthOfBridge: Length[Bridge] =
     |   new Length[Bridge] {
     |     def lengthOf(b: Bridge): Long = b.span
     |   }
lengthOfBridge: org.scalatest.enablers.Length[Bridge] = $anon$1@3fa27a4a

With the implicit Length[Bridge] in scope, you can now use ScalaTest's should have length syntax with Bridge instances:

scala> bridge should have length 2000
res4: org.scalatest.Assertion = Succeeded

scala> bridge should have length 2001
org.scalatest.exceptions.TestFailedException: Bridge(2000) had length 2000 instead of expected length 2001
  at org.scalatest.MatchersHelper$.newTestFailedException(MatchersHelper.scala:148)
  at org.scalatest.MatchersHelper$.indicateFailure(MatchersHelper.scala:366)
  at org.scalatest.Matchers$ResultOfHaveWordForExtent.length(Matchers.scala:2720)
  ... 43 elided

Source
Length.scala
Linear Supertypes
AnyRef, Any
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. Length
  2. AnyRef
  3. Any
  1. Hide All
  2. Show All
Visibility
  1. Public
  2. All

Abstract Value Members

  1. abstract def lengthOf(obj: T): Long

    Permalink

    Returns the length of the passed object.

    Returns the length of the passed object.

    obj

    the object whose length to return

    returns

    the length of the passed object

Concrete Value Members

  1. final def !=(arg0: Any): Boolean

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

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

    Permalink
    Definition Classes
    AnyRef → Any
  4. final def asInstanceOf[T0]: T0

    Permalink
    Definition Classes
    Any
  5. def clone(): AnyRef

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

    Permalink
    Definition Classes
    AnyRef
  7. def equals(arg0: Any): Boolean

    Permalink
    Definition Classes
    AnyRef → Any
  8. def finalize(): Unit

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

    Permalink
    Definition Classes
    AnyRef → Any
  10. def hashCode(): Int

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

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

    Permalink
    Definition Classes
    AnyRef
  13. final def notify(): Unit

    Permalink
    Definition Classes
    AnyRef
  14. final def notifyAll(): Unit

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

    Permalink
    Definition Classes
    AnyRef
  16. def toString(): String

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

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

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

    Permalink
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )

Inherited from AnyRef

Inherited from Any

Ungrouped