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
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Abstract Value Members
- abstract def lengthOf(obj: T): Long
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
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