Class

org.scalatest.matchers

LazyArg

Related Doc: package matchers

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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)

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    arg

    the argument

    f

    a function that given the arg will produce a String

Value Members

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

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    Definition Classes
    AnyRef → Any

  2. final def ##(): Int

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    Definition Classes
    AnyRef → Any

  3. final def ==(arg0: Any): Boolean

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    Definition Classes
    AnyRef → Any

  4. val arg: Any

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    the argument

  5. final def asInstanceOf[T0]: T0

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    Definition Classes
    Any

  6. def clone(): AnyRef

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    Attributes
    protected[java.lang]
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    AnyRef
    Annotations
    @throws( ... )

  7. final def eq(arg0: AnyRef): Boolean

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    Definition Classes
    AnyRef

  8. def finalize(): Unit

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    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )

  9. final def getClass(): Class[_]

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    Definition Classes
    AnyRef → Any

  10. final def isInstanceOf[T0]: Boolean

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    Definition Classes
    Any

  11. final def ne(arg0: AnyRef): Boolean

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    Definition Classes
    AnyRef

  12. final def notify(): Unit

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    Definition Classes
    AnyRef

  13. final def notifyAll(): Unit

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    Definition Classes
    AnyRef

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

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    Definition Classes
    AnyRef

  15. def toString(): String

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    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

  16. final def wait(): Unit

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    Definition Classes
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    @throws( ... )

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

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    AnyRef
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    @throws( ... )

  18. final def wait(arg0: Long): Unit

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    Definition Classes
    AnyRef
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    @throws( ... )