org.scalatest.matchers

LazyArg

final case class LazyArg(arg: Any)(f: (Any) ⇒ String) extends Product with Serializable

Transforms a given object's toString with a given function lazily.

This class is intended to be used with the mapResult method of MatcherProducers, which you can use to modify error messages when composing matchers. This class exists to enable those error messages to be modified lazily, so that toString is invoked on the given arg, and its result transformed by the given function f, only when and if the toString method is invoked on the LazyArg. As a performance optimization, ScalaTest's MatchResult avoids invoking toString on objects until and unless an error message is actually needed, to minimize unecessary creation and concatenation of strings. The LazyArg class enables this same performance optimization when composing matchers.

The other design goal of LazyArg is to make the internal arg available for inspection in an IDE. In a future version of ScalaTest, the args of MatchResult that were used to create the error message will be included in the TestFailedException, so they can be inspected in IDEs. This is why the arg field of LazyArg is public.

For an example of using LazyArg, see the Composing matchers section in the main documentation for trait Matcher.

arg

the argument

f

a function that given the arg will produce a String

Source
LazyArg.scala
Linear Supertypes
Serializable, Serializable, Product, Equals, AnyRef, Any
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Instance Constructors

  1. new LazyArg(arg: Any)(f: (Any) ⇒ String)

    arg

    the argument

    f

    a function that given the arg will produce a String

Value Members

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

    Definition Classes
    AnyRef
  2. final def !=(arg0: Any): Boolean

    Definition Classes
    Any
  3. final def ##(): Int

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

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

    Definition Classes
    Any
  6. val arg: Any

    the argument

  7. final def asInstanceOf[T0]: T0

    Definition Classes
    Any
  8. def clone(): AnyRef

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

    Definition Classes
    AnyRef
  10. def finalize(): Unit

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

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

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

    Definition Classes
    AnyRef
  14. final def notify(): Unit

    Definition Classes
    AnyRef
  15. final def notifyAll(): Unit

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

    Definition Classes
    AnyRef
  17. def toString(): String

    Returns the result of invoking the function f, passed to the LazyArg constructor, on field arg.

    Returns the result of invoking the function f, passed to the LazyArg constructor, on field arg.

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

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

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

    Definition Classes
    AnyRef
    Annotations
    @throws()

Inherited from Serializable

Inherited from Serializable

Inherited from Product

Inherited from Equals

Inherited from AnyRef

Inherited from Any

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