Trait/Object

com.thoughtworks.feature

Factory

Related Docs: object Factory | package feature

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trait Factory[Output] extends Serializable

A factory to create new instances, especially dynamic mix-ins.

Author:

杨博 (Yang Bo) <[email protected]>

Source
Factory.scala
Examples:
  1. Given a trait that has abstract members.

    trait Foo {
      val myValue: String
      var myVariable: Long
      def myMethod0(): Option[Double]
      def myMethod2(p0: Int, p1: Int): Int
      def myCurriedMethod(seq: Seq[Int])(mapper: Int => String): Seq[String]
      // Methods without pararmeters is disabled for now, due to https://github.com/scala/bug/issues/10647
      // def myByNameMethod: Option[Int]
    }

    When creating a factory for the trait.

    val factory = Factory[Foo]

    Then the newInstance method of the factory should accept named arguments according to abstract members.

    val createdFromNamedArguments: Foo = factory.newInstance(
      myValue = "string value",
      myVariable = 42L,
      myMethod0 = () => Some(0.5),
      myMethod2 = _ + _,
      myCurriedMethod = seq => mapper => seq.map(mapper)
    )
    createdFromNamedArguments.myValue should be("string value")
    createdFromNamedArguments.myVariable should be(42L)
    createdFromNamedArguments.myMethod0() should be(Some(0.5))
    createdFromNamedArguments.myMethod0() shouldNot be theSameInstanceAs createdFromNamedArguments.myMethod0()
    createdFromNamedArguments.myMethod2(1000, 24) should be(1024)
    createdFromNamedArguments.myCurriedMethod(Seq(2, 3, 4))(_.toString) should be(Seq("2", "3", "4"))

    When using unnamed parameters, the parameters should be passed in alphabetical order

    val createdFromUnnamedArguments: Foo = factory.newInstance(
      seq => mapper => seq.map(mapper), // myCurriedMethod
      () => Some(0.5),                  // myMethod0
      _ + _,                            // myMethod2
      "string value",                   // myValue
      42L                               // myVariable
    )
  2. ,
  3. Given two traits that have no abstract member.

    trait Foo
    trait Bar

    When creating a factory for mix-in type of the two types.

    val factory = Factory[Foo with Bar]

    Then the newInstance method of the factory should accept no parameters.

    val fooBar: Foo with Bar = factory.newInstance()
    fooBar should be(a[Foo])
    fooBar should be(a[Bar])
  4. ,
  5. Given a trait that contains an abstract method annotated as @inject.

    import com.thoughtworks.feature.Factory.inject
    trait Foo[A] {
      @inject def orderingA: Ordering[A]
    }

    When creating a factory for the trait

    val factory = Factory[Foo[Int]]

    Then the @inject method will be replaced to an implicit value.

    val foo = factory.newInstance()
    foo.orderingA should be(implicitly[Ordering[Int]])

    It will not compile if no implicit value found. For example, Foo[Symbol] requires an implicit value of type Ordering[Symbol], which is not availble.

    "Factory[Foo[Symbol]]" shouldNot compile

    If the trait does not contain abstract methods other than @inject methods, then the factory type class is a Factory.Factory0, which can be summoned by Predef.implicitly,

    val nullaryFactory = implicitly[Factory.Factory0[Foo[Int]]]

    and newInstance method is available on the Factory.Factory0 as well.

    nullaryFactory.newInstance().orderingA should be(implicitly[Ordering[Int]])
Note

However, if the nested type is an alias to another type outside of the type to create, then it is allowed

trait Outer {
  type Inner = String
  val inner: Option[Inner]
}
val outer: Outer = Factory[Outer].newInstance(inner = Some("my value"))
outer.inner should be(Some("my value"))
,

This Factory disallows creating types that has an abstract member whose type depends on nested types. Given an abstract val inner whose type is the Inner,

trait Outer {
  trait Inner
  val inner: Option[Inner]
}

then the attempt to create factory for Outer, like Factory[Outer].newInstance(inner = None), will cause a value inner has incompatible type compile error.

,

@inject works on implicit abstract methods as well.

import com.thoughtworks.feature.Factory.inject
trait Foo[A] {
  @inject implicit def orderingA: Ordering[A]
}
Factory[Foo[Int]].newInstance().orderingA should be(implicitly[Ordering[Int]])
,

Factories may be nested

import com.thoughtworks.feature.Factory.inject
import com.thoughtworks.feature.Factory.Factory1
import com.thoughtworks.feature.ByName.`=>`
trait Outer {
  trait AbstractParameterApi
  type AbstractParameter <: AbstractParameterApi
  trait InnerApi {
    def foo: AbstractParameter
  }
  type Inner <: InnerApi
  @inject val innerFactory: Factory1[`=>`[AbstractParameter], Inner]
}
val outer = Factory[Outer].newInstance()
outer.innerFactory.newInstance(new outer.AbstractParameterApi {}) should be(an[outer.Inner])
,

Factories may create types that contains refinement types

trait SomeBuilder {
  type A
  def makeSome(a: A) = Some(a)
}
val someBuilder = Factory[SomeBuilder { type A = Int }].newInstance()
someBuilder.makeSome(42) should be(Some(42))
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Inherited
  1. Factory
  2. Serializable
  3. Serializable
  4. AnyRef
  5. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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Visibility
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Type Members

  1. abstract type Constructor

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    A function type that returns Output.

    A function type that returns Output.

    The parameter types are all abstract members in Output

Abstract Value Members

  1. abstract val newInstance: Constructor

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    Returns an instance of Output, which overrides abstract members in Output according to parameters pass to this newInstance method.

Concrete 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. def +(other: String): String

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    Implicit information
    This member is added by an implicit conversion from Factory[Output] to any2stringadd[Factory[Output]] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  4. def ->[B](y: B): (Factory[Output], B)

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    Implicit information
    This member is added by an implicit conversion from Factory[Output] to ArrowAssoc[Factory[Output]] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  5. final def ==(arg0: Any): Boolean

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    Definition Classes
    AnyRef → Any
  6. final def asInstanceOf[T0]: T0

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    Definition Classes
    Any
  7. def clone(): AnyRef

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    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  8. def ensuring(cond: (Factory[Output]) ⇒ Boolean, msg: ⇒ Any): Factory[Output]

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    Implicit information
    This member is added by an implicit conversion from Factory[Output] to Ensuring[Factory[Output]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  9. def ensuring(cond: (Factory[Output]) ⇒ Boolean): Factory[Output]

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    Implicit information
    This member is added by an implicit conversion from Factory[Output] to Ensuring[Factory[Output]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  10. def ensuring(cond: Boolean, msg: ⇒ Any): Factory[Output]

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    Implicit information
    This member is added by an implicit conversion from Factory[Output] to Ensuring[Factory[Output]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  11. def ensuring(cond: Boolean): Factory[Output]

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    Implicit information
    This member is added by an implicit conversion from Factory[Output] to Ensuring[Factory[Output]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  12. final def eq(arg0: AnyRef): Boolean

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

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    Definition Classes
    AnyRef → Any
  14. def finalize(): Unit

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    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  15. def formatted(fmtstr: String): String

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    Implicit information
    This member is added by an implicit conversion from Factory[Output] to StringFormat[Factory[Output]] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  16. final def getClass(): Class[_]

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    Definition Classes
    AnyRef → Any
  17. def hashCode(): Int

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

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

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

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

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

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    Definition Classes
    AnyRef
  23. def toString(): String

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

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

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

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    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  27. def [B](y: B): (Factory[Output], B)

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    Implicit information
    This member is added by an implicit conversion from Factory[Output] to ArrowAssoc[Factory[Output]] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

Inherited from Serializable

Inherited from Serializable

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd from Factory[Output] to any2stringadd[Factory[Output]]

Inherited by implicit conversion StringFormat from Factory[Output] to StringFormat[Factory[Output]]

Inherited by implicit conversion Ensuring from Factory[Output] to Ensuring[Factory[Output]]

Inherited by implicit conversion ArrowAssoc from Factory[Output] to ArrowAssoc[Factory[Output]]

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