Package net.jqwik.api.state

Interface Transformer<T>

Type Parameters:
T - The type of state to be transformed in a chain
All Superinterfaces:
Function<@NonNull T,@NonNull T>
Functional Interface:
This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
@FunctionalInterface @API(status=EXPERIMENTAL, since="1.7.0") public interface Transformer<T> extends Function<@NonNull T,@NonNull T>
A transformer is used to transform a state of type T into another value of this type. Transformation can create a new object, or change the inner state of an object and return it.

In addition to performing a state transformation the mutator function can also check or assert conditions and invariants that should hold when doing the transformation. This is especially useful when a transformer is used as part of an action.

See Also:

  • Field Details

    • END_OF_CHAIN

      static final Transformer<?> END_OF_CHAIN
      The singleton object used for all calls to endOfChain().

    • NOOP

      static final Transformer<?> NOOP
      The singleton object used for all calls to noop().

  • Method Details

    • endOfChain

      static <T> Transformer<T> endOfChain()
      Use this transformer to stop further enhancement of a chain.

      Whenever a endOfChain() is chosen by a chain, the chain ends with the current state being provided (e.g. in the chain's iterator) for a last time.

      Type Parameters:
      T - The transformer's state value type
      Returns:
      a transformer instance

    • noop

      static <T> Transformer<T> noop()
      Use this transformer to signal a noop transformation. This can be useful when a Transformation wants to provide a transformer that does nothing in some circumstances.

      Noop transformers are ignored and not added to the chain of transformers.

      Type Parameters:
      T - The transformer's state value type
      Returns:
      a transformer instance

    • transform

      static <S> Transformer<S> transform(String description, Function<S,S> transform)
      Create a transformer with a description
      Type Parameters:
      S - The type of the state to transform
      Parameters:
      description - A text to describe what the transform is doing
      transform - The actual transforming function
      Returns:
      a new instance of a transformer

    • mutate

      static <S> Transformer<S> mutate(String description, Consumer<S> mutate)
      Convenience method to create a transformer with a description. A mutator works on a mutable, stateful object which will always be returned.
      Type Parameters:
      S - The type of the state to mutate
      Parameters:
      description - A text to describe what the transform is doing
      mutate - The actual mutating operation
      Returns:
      a new instance of a transformer

    • transformation

      default String transformation()
      Describe the transformation this Transformer is doing in a human understandable way.
      Returns:
      non-empty String

    • isEndOfChain

      default boolean isEndOfChain()