Implicits can be used to declare a value to be provided as a default as long as an implicit value is set with in the scope.
Implicits can be used to declare a value to be provided as a default as long as an implicit value is set with in the scope. These are called implicit function parameters:
convertTypeImplicits
convertTypeImplicits
Implicits can be used to automatically convert one type to another
Default arguments though are preferred to Implicit Function Parameters
The actual arguments that are eligible to be passed to an implicit parameter fall into two categories: * First, eligible are all identifiers x that can be accessed at the point of the method call without a prefix and that denote an implicit definition or an implicit parameter.
The actual arguments that are eligible to be passed to an implicit parameter fall into two categories: * First, eligible are all identifiers x that can be accessed at the point of the method call without a prefix and that denote an implicit definition or an implicit parameter. * Second, eligible are also all members of companion modules of the implicit parameter's type that are labeled implicit.
In the following example we define a method sum which computes the sum of a list of elements using the monoid's add and unit operations. Please note that implicit values can not be top-level, they have to be members of a template.
abstract class SemiGroup[A] { def add(x: A, y: A): A } abstract class Monoid[A] extends SemiGroup[A] { def unit: A } object ImplicitTest extends App { implicit object StringMonoid extends Monoid[String] { def add(x: String, y: String): String = x concat y def unit: String = "" } implicit object IntMonoid extends Monoid[Int] { def add(x: Int, y: Int): Int = x + y def unit: Int = 0 } def sum[A](xs: List[A])(implicit m: Monoid[A]): A = if (xs.isEmpty) m.unit else m.add(xs.head, sum(xs.tail)) println(sum(List(1, 2, 3))) println(sum(List("a", "b", "c"))) }
Here is the output of the Scala program:
6
abc
Implicits wrap around existing classes to provide extra functionality. This is similar to *monkey patching* in **Ruby**, and *Meta-Programming* in **Groovy**.
Creating a method isOdd for Int, which doesn't exist:
Implicits rules can be imported into your scope with an import:
Implicit Function Parameters can contain a list of implicits:
This method has been deprecated in favor of macro assertion and will be removed in a future version of ScalaTest. If you need this, please copy the source code into your own trait instead.
This method has been deprecated in favor of macro assertion and will be removed in a future version of ScalaTest. If you need this, please copy the source code into your own trait instead.
This method has been deprecated in favor of macro assumption and will be removed in a future version of ScalaTest. If you need this, please copy the source code into your own trait instead.
This method has been deprecated in favor of macro assumption and will be removed in a future version of ScalaTest. If you need this, please copy the source code into your own trait instead.
Please use 'an [Exception] should be thrownBy { ... }' syntax instead
This expect method has been deprecated. Please replace all invocations of expect with an identical invocation of assertResult instead.
This expect method has been deprecated. Please replace all invocations of expect with an identical invocation of assertResult instead.
This expectResult method has been deprecated. Please replace all invocations of expectResult with an identical invocation of assertResult instead.
This expectResult method has been deprecated. Please replace all invocations of expectResult with an identical invocation of assertResult instead.