Lens

public struct Lens<A, B>

Enables read and copy-on-write access for an entity’s property in a datastructure.

Some examples can be found in this blog post.

  • Serves as getter.

    Declaration

    Swift

    public let from: (A) -> B
  • to

    Serves as setter.

    Declaration

    Swift

    public let to: (B, A) -> A

  • Creates a lens.

    Parameter

    Parameter from: Returns a property from a given value.

    Parameter

    Parameter of: Sets a property to a given value.

    Declaration

    Swift

    public init(from: @escaping (A) -> B, to: @escaping (B, A) -> A)

    Parameters

    from

    Returns a property from a given value.
    of

    Sets a property to a given value.

  • Creates a new lens by using a child lens.

    Parameter

    Parameter lens: The lens to be used as child of self.

    Returns

    A new lens from the current type to the given.

    Declaration

    Swift

    public func child<C>(with lens: Lens<B, C>) -> Lens<A, C>

    Parameters

    lens

    The lens to be used as child of self.

    Return Value

    A new lens from the current type to the given.

  • Creates a new lens by using a child lens. Convenience method for Lens.child(lens:).

    Parameter

    Parameter from: Lens.from to be used as a child-

    Parameter

    Parameter to: Lens.to to be used as a child-

    Returns

    A new lens from the current type to the given.

    Declaration

    Swift

    public func child<C>(from: @escaping (B) -> C, to: @escaping (C, B) -> B) -> Lens<A, C>

    Parameters

    from

    Lens.from to be used as a child-
    to

    Lens.to to be used as a child-

    Return Value

    A new lens from the current type to the given.

  • Creates a new lens by using a child lens. Reversed convenience method for Lens.child(lens:).

    Parameter

    Parameter lens: The lens to be used as parent of self.

    Returns

    A new, combined lens.

    Declaration

    Swift

    public func asChild<S>(of parent: Lens<S, A>) -> Lens<S, B>

    Parameters

    lens

    The lens to be used as parent of self.

    Return Value

    A new, combined lens.

  • Creates a new lens by using a child lens. Reversed convenience method for Lens.child(lens:).

    Parameter

    Parameter lens: The lens to be used as parent of self.

    Returns

    A new, combined lens.

    Declaration

    Swift

    public func asChild<S>(from: @escaping (S) -> A, to: @escaping (A, S) -> S) -> Lens<S, B>

    Parameters

    lens

    The lens to be used as parent of self.

    Return Value

    A new, combined lens.