trait Size[T] extends AnyRef
Supertrait for Size
typeclasses.
Trait Size
is a typeclass trait for objects that can be queried for size.
Objects of type T for which an implicit Size[T]
is available can be used
with the should have size
syntax.
In other words, this trait enables you to use the size checking
syntax with arbitrary objects. As an example, the following Bridge
class:
scala> import org.scalatest._ import org.scalatest._ scala> import enablers.Size import enablers.Size 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 size
syntax with Bridge
,
because ScalaTest doesn't know that a bridge's span means its size:
scala> val bridge = new Bridge(2000) bridge: Bridge = Bridge(2000) scala> bridge should have size 2000 <console>:34: error: could not find implicit value for parameter sz: org.scalatest.enablers.Size[Bridge] bridge should have size 2000 ^
You can teach this to ScalaTest, however, by defining an implicit Size[Bridge]
.
scala> implicit val sizeOfBridge: Size[Bridge] = | new Size[Bridge] { | def sizeOf(b: Bridge): Long = b.span | } sizeOfBridge: org.scalatest.enablers.Size[Bridge] = $anon$1@3fa27a4a
With the implicit Size[Bridge]
in scope, you can now use ScalaTest's should have size
syntax with Bridge
instances:
scala> bridge should have size 2000 res4: org.scalatest.Assertion = Succeeded scala> bridge should have size 2001 org.scalatest.exceptions.TestFailedException: Bridge(2000) had size 2000 instead of expected size 2001 at org.scalatest.MatchersHelper$.newTestFailedException(MatchersHelper.scala:148) at org.scalatest.MatchersHelper$.indicateFailure(MatchersHelper.scala:366) at org.scalatest.Matchers$ResultOfHaveWordForExtent.size(Matchers.scala:2720) ... 43 elided
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- Size.scala
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abstract
def
sizeOf(obj: T): Long
Returns the size of the passed object.
Returns the size of the passed object.
- obj
the object whose size to return
- returns
the size of the passed object
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