Add Ref.lens constructor #827
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Some discussion on Gitter about the semantics (changes to A that don't involve changes in B): https://gitter.im/typelevel/cats-effect-dev?at=5e8b0e65d021c45cc7c995a6 |
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I was looking at https://github.com/oleg-py/meow-mtl recently and I believe it covers your use case. It will both derive a Of course |
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@rkrzewski we're using meow-mtl as well, the problem is that |
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@djspiewak @SystemFw thoughts? I think this belongs here, but I remember you had different opinions on it |
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On balance, I like it and I'd like to see it included |
| @@ -226,6 +226,23 @@ object Ref { | |||
| */ | |||
| def unsafe[F[_], A](a: A)(implicit F: Sync[F]): Ref[F, A] = new SyncRef[F, A](new AtomicReference[A](a)) | |||
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| /** | |||
| * Creates an instance focused on a component of another Ref's value. | |||
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I think we should briefly mention that updates in the parent that don't change the child won't disable the setter in the child's access.
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Hey @djspiewak, any chance we can release this soon? |
I find
Ref.lensuseful in tests, where a singleRefaggregating state of multiple mocks can be transformed into a few "focused"Refs, ready for use in the mocks.I'm not sure, though, if it should be a part of
cats-effector rather some small satellite library, so I'll leave it up to you to decide 😉